The Project Gutenberg EBook of The Library of Work and Play: Mechanics, Indoors and Out, by Fred T. Hodgson This eBook is for the use of anyone anywhere at no cost and with almost no restrictions whatsoever. You may copy it, give it away or re-use it under the terms of the Project Gutenberg License included with this eBook or online at www.gutenberg.org Title: The Library of Work and Play: Mechanics, Indoors and Out Author: Fred T. Hodgson Release Date: March 8, 2014 [EBook #45083] Language: English Character set encoding: UTF-8 *** START OF THIS PROJECT GUTENBERG EBOOK LIBRARY OF WORK AND PLAY: MECHANICS *** Produced by Chris Curnow, Chris Jordan and the Online Distributed Proofreading Team at http://www.pgdp.net (This file was produced from images generously made available by The Internet Archive) THE CHILDREN'S LIBRARY OF WORK AND PLAY. Mechanics, Indoors and Out THE CHILDREN'S LIBRARY OF WORK AND PLAY CARPENTRY AND WOODWORK By Edwin W. Foster ELECTRICITY AND ITS EVERYDAY USES By John F. Woodhull, Ph.D. GARDENING AND FARMING By Ellen Eddy Shaw HOME DECORATION By Charles Franklin Warner, Sc.D. HOUSEKEEPING By Elizabeth Hale Gilman MECHANICS, INDOORS AND OUT By Fred T. Hodgson NEEDLECRAFT By Effie Archer Archer OUTDOOR SPORTS, AND GAMES By Claude H. Miller, Ph.B. OUTDOOR WORK By Mary Rogers Miller WORKING IN METALS By Charles Conrad Sleffel Photograph by Underwood & Underwood A MOTOR BOAT MODEL "In the making of little models of this kind, you will encounter many things that will tax your skill and ingenuity, as amateur workmen." Title Page MECHANICS, INDOORS AND OUT BY FRED T. HODGSON GARDEN CITY NEW YORK DOUBLEDAY, PAGE & COMPANY 1911 ALL RIGHTS RESERVED, INCLUDING THAT OF TRANSLATION INTO FOREIGN LANGUAGES, INCLUDING THE SCANDINAVIAN COPYRIGHT, 1911, BY DOUBLEDAY, PAGE & COMPANY ACKNOWLEDGMENT THE PUBLISHERS WISH TO ACKNOWLEDGE THEIR INDEBTEDNESS TO THE HORACE MANN SCHOOL FOR THEIR COURTESY IN PERMITTING certain of the photographs to be taken for this volume. CONTENTS PART I CHAPTER PAGE I. A Pathway of Cement Purchasing property, River Passaic—Removing rocks and other obstacles—Preparing for cement sidewalk—Digging trench and purchasing materials—Making, laying, and properly placing concrete —The lever and roller and application—Moving heavy bodies with lever and roller—Finishing the cement sidewalk—How to make good concrete walks. 3 II. Building of a Boat House Qualities of the inclined plane—Dismantling an old barn and out-houses—Blocks and tackle, ropes and pulleys—Strength and care of ropes—Building a boat-house, using old materials—Strength of timber floors—Method of construction—Holding power of nails—Doors and windows for boat- house—The use of rollers in moving heavy weights—Sliding ways for boat—How heavy stones were raised to tops of Egyptian Pyramids. 36 III. Bridge and Boat Work Dimensions of the launch—Arrival of The Mocking-Bird—An interesting boat talk—A sail on the river—Building a small foot-bridge—The same completed—Some rules for sailing a launch— Fitting up boat-house and dock—Preparing block for keel—The winch and its construction—The wheel and axle as a mechanical power—The fusee, and what it means—Some problems solved. 65 IV. Making a Gasolene Launch Arrival of boat material—Laying keel and keelson—Setting up the boat and giving her shape— Laying engine bed—Installing engine and propeller—Nailing on planking—Table of offsets— Gasolene engine and carburetor—Dimensions of engine and propeller—Gas engines, generally— Danger of using gasolene—The proper use of yacht flags for signalling. 84 V. A Talk About Engines Water around the cylinder—The carburetor and spark coil—Running the engine in boat-house— Varnishing the boat—A steamboat on the river—A story of the first steam engine—How the steam acted in the case—The slide valve, piston and steam chest—Internal and external engine heaters— Horse-power and how calculated—Foot pounds, dry steam and condensation—Expansion of gases, turbines—Gilding the name—Constructing picnic tables and seats—Height of tables, chairs and benches. 110 VI. Propeller and Other Screws The launch of the Caroline—Trial of the new boat—Description of the screw as a power—The wheel and worm and endless screw—Formula for counting power of wheel and worm screws of various kinds—Archimedian screw and water lifter—Some data of power of "wheel and worm"— The screw propeller, with data—How to calculate force of propeller screws—Finding pitch and other lines for propeller—The screw auger or boring tool—Adhesion of ordinary wood screws— How to loosen and withdraw rusty screws. 136 VII. Aeroplanes Seats for riverside—Model aeroplane for the "Fourth"—Dimension on construction of planes— Why a monoplane rises from the earth—The gyroscope as a balancer—The biplane and its construction—Aeroplanes generally—The French aeroplane "Demoiselle"—How to make a model aeroplane—Illustrations and details of model aeroplane—Some general remarks. 158 VIII. Kites, Sundials, Patents The theory of kite-flying—The highest kite ascent—The flat plane kite—The kite a small aeroplane —A box kite of common type—Cellular kites of various kinds—Pairs and bevies of kites—Bird flight and motion—War kites of various kinds—Wind gauges and wind force—Patents and how to secure them—A simple sundial—How to make an oval flower bed. 185 IX. Tides The "why" of the tides explained—Globular form of the earth proved—Day and night—Phases of the moon—Attraction of the sun and moon—Newton's theory of the tides—Height of tides—A simple hygrometer—The Australian boomerang—Theory of the pump. 212 X. Wall Making and Plumbing Protecting the river bank—Concrete retaining walls—Big dams in the West—Galveston sea wall— The great dam across the Nile—Proposed irrigation works in Babylon—Some properties of light and sound—Hints on amateur plumbing—The peppermint test—Barometers of various kinds— Thermometers, and their uses—Something about steel springs—How to make a cross-bow—The gyroscope and its uses. 237 PART II I. Some Practical Advice The inventor, ancient and modern—Barriers to mechanical progress in the past—Laws of gravitation—How to adjust sewing machines. 271 II. Mechanical Movements Coffee mills—Pulleys—Pumps—Pistons—Levers—Steam engine and water wheel governors, etc. 306 III. The Weather and Indoor Work How to make a rain gauge—Hail—Snow—Designing, making and inflating paper balloons— Magnetized watches—A boy's wheelbarrow—Vacuum cleaners. 349 IV. Motors and Typewriters Motors, gasolene and steam—Automobile frames—The modern typewriter—Directions for securing copyrights. 387 ILLUSTRATIONS A Motor-Boat Model Frontispiece FACING PAGE Boat-House and Workshop 42 The Creek 70 Making a Motor Launch 88 Finishing the Motor Launch 112 The Monoplane Model Complete 160 Making an Aeroplane Model 180 Making Kites 190 A Sundial Made of Concrete 208 PART I I I A PATHWAY OF CEMENT DO wish papa would buy the land from Mr. Breigel. The weather will soon be fine enough to play out of doors!" SO SAID JESSIE GREGG, A ROSY-CHEEKED GIRL OF TWELVE, TO HER ELDEST BROTHER, FRED, ONE EVENING IN MARCH, AS THEY STOOD IN THE PORCHWAY OF THEIR HOME, SITUATED NEAR THE BANK OF THE PASSAIC RIVER, A FEW MILES FROM THE CITY IN WHICH MR. GREGG had his business offices. "Why, Jessie," said Fred, "papa told me this morning, at breakfast, he expected to close the deal, that is, get the deed of THE PROPERTY, THIS AFTERNOON. I AM JUST AS ANXIOUS AS YOU ARE TO HAVE THE MATTER SETTLED, FOR IF HE GETS THE LAND, I WILL HAVE A LOT OF WORK TO DO, AND I WANT TO COMMENCE IT RIGHT AWAY. THE LAND MUST BE OURS, FOR PAPA IS LATER THAN USUAL THIS evening. Oh! there's the train just coming in; he will be here in a few minutes, and then we'll know." "OH, FRED! HE AND GEORGE ARE COMING NOW. I SEE THEM AT THE TURN OF THE ROAD. I'LL RUN TO MEET THEM." AWAY SHE SCAMPERED, AND ALMOST UPSET HER FATHER BY JUMPING INTO HIS ARMS, AS SHE WAS QUITE A PLUMP, HUSKY GIRL AND EVIDENTLY A pet, for her father kissed her fervently as she slid from his arms to the ground. Then the three trudged homeward. "Jessie," said George, a younger brother, "I have a secret for you if you won't tell Fred, until papa has told him." "What is it?" "Papa has bought the land, and has got it in his pocket." "Oh! I am so glad," said Jessie, "but how can he have it in his pocket." "GEORGE MEANS THAT I HAVE THERE THE PAPERS, DEEDS, CONVEYANCES, AND RECEIPTS, GIVING ME THE SOLE OWNERSHIP OF THE LAND, AND ALL THAT IS ON IT, INCLUDING THE TREES, OLD BARN, AND OTHER STRUCTURES; SO, GIRLIE, YOU CAN GET DOWN TO THE RIVER NOW without having to climb a fence." FRED MET HIS FATHER ON HIS ARRIVAL AT THE HOUSE, BUT WAS TOO WELL BEHAVED TO ASK HIM ABOUT THE LAND, THOUGH HE WAS AS ANXIOUS TO KNOW AS HE COULD BE. HIS FATHER SAW THE BOY'S ANXIETY AND AFTER TEA ASKED HIM TO GO WITH HIM INTO HIS DEN, A LITTLE ROOM NICELY FIXED UP SOME TIME PREVIOUS, CONTAINING MANY ARTICLES OF WOOD, BRASS, AND PLASTER OF PARIS, FRED AND GEORGE HAD MADE DURING THE PAST WINTER. JESSIE, ALSO, HAD CONTRIBUTED MANY LITTLE THINGS TOWARD THE DECORATION OF "THE LION'S DEN," AS SHE CALLED THE ROOM INTO WHICH HER FATHER RETIRED TO HAVE HIS EVENING SMOKE, TO TAKE A FRIEND, OR TO DO A little private business. WHEN SEATED, MR. GREGG CALLED FRED TO HIS DESK, AND TALKED OVER SOME HOME AFFAIRS BEFORE HE SAID: "NOW, MY BOY, SINCE I HAVE SECURED THE PROPERTY BEHIND US, AS YOU CHILDREN DESIRED, I SHALL EXPECT YOU AND GEORGE TO HELP BY YOUR LABOUR, AND BY THE KNOWLEDGE YOU OBTAINED AT THE TRAINING SCHOOL, IN MAKING THE IMPROVEMENTS ON THE LAND AND THE WATER FRONT WE HAVE TALKED OF SO OFTEN. I AM SURE, WITH MY ADVICE AND ASSISTANCE, YOU WILL BE ABLE TO DO MOST OF THE WORK, OR AT LEAST TO SUPERINTEND IT IN SUCH A WAY THAT THE LABOUR AND EXPENDITURE WILL NOT BE WASTED. YOU KNOW, FRED, I am not a rich man, so cannot afford to waste money on experiments." "INDEED, FATHER," SAID FRED, "I WILL DO ALL I CAN. YOU MAY COUNT ON MY GIVING MY BEST ATTENTION TO WHATEVER WORK AND improvements you entrust me with." "THAT IS WELL SAID, MY BOY, AND WHAT I EXPECTED FROM YOU. WE WILL BEGIN OPERATIONS BY PUTTING DOWN A CEMENT PATHWAY FROM THE WALK NOW LEADING TO THE HOUSE FROM THE STREET, AND CONTINUE IT TO THE RIVER, WHERE YOU MUST BUILD A SMALL BOAT HOUSE AND WORKSHOP, AS I INTEND EITHER TO PURCHASE A SMALL GASOLINE LAUNCH FOR OUR OWN USE, OR HAVE YOU BUILD ONE, IF you feel equal to that." "OH! FATHER, YOU ARE SO GOOD," SAID FRED. "THERE IS NOTHING I'D LIKE BETTER THAN TO DO THIS WORK, AND PARTICULARLY TO BUILD A BOAT. I'M SURE I CAN DO THAT WITH YOUR HELP AND ADVICE. AS TO PUTTING DOWN THE PATHWAY, THAT I CAN DO VERY WELL, AFTER my good training in cement works." "ALL RIGHT, MY SON. WE'LL SEE IN THE MORNING WHAT OLD MATERIAL WE HAVE ON THE TWO PLACES WHICH CAN BE USED. THERE MUST BE QUITE A QUANTITY OF LUMBER, TIMBER, BRICKS, HARD MORTAR, AND PLASTER IN AND ABOUT THE OLD BARN AND THE SMALLER buildings." THE NEXT MORNING GEORGE EVIDENTLY HAD SOMETHING ON HIS MIND, AND SEEMED TO BE ON THE POINT OF EXPLOSION. MRS. GREGG noticed this and said to him, "Why are you so restless this morning? Why don't you finish your breakfast?" "OH! MOTHER," HE EXCLAIMED, "I AM TOO GLAD. I AM SO FULL OF THE GOOD THINGS FRED TOLD ME LAST NIGHT AND THIS MORNING I haven't any room for breakfast." "What did Fred say to you?" asked the mother. "OH! HE TOLD ME HE WAS GOING TO BUILD A CEMENT WALK RIGHT FROM THE DOOR HERE TO THE RIVER, AND DO LOTS OF OTHER THINGS; AND BEST OF ALL, MOTHER, HE IS GOING TO BUILD A BOAT, A REAL BOAT, THAT WILL BE DRIVEN BY A GASOLINE ENGINE, JUST LIKE WALTER Scott's. That will be glorious! I can take you and Jessie up the river to Belville to see aunty, whenever you want to go." "Very well, George; we will see about that after the boat is ready to take on passengers." BREAKFAST OVER, THE WHOLE FAMILY WALKED OUT TO SEE THE NEWLY ACQUIRED PROPERTY. THEY HAD ALL SEEN AND WALKED OVER THE grounds often, but never before with that feeling of pride in ownership which possession creates. [3] [4] [5] [6] [7] AS THERE COULD BE NO OBJECTION TO THE REMOVAL OF THE LINE FENCE BETWEEN THE NEWLY ACQUIRED PROPERTY AND THE HOMESTEAD, FRED GOT A HANDSAW, AND CUT DOWN A PART OF IT, MAKING AN OPENING SOME NINE OR TEN FEET WIDE, SO THAT ALL could pass into the new place without climbing or stumbling. THE OLD BARN WAS THE FIRST THING EXAMINED, AND IT WAS FOUND TO BE IN A STATE OF GOOD PRESERVATION, AND QUITE LARGE. IT HAD BEEN BUILT—PERHAPS IN COLONIAL TIMES—OF HEAVY TIMBER, OAK, CHESTNUT, AND PINE, AND IT CONTAINED ENOUGH TIMBER AND LUMBER TO BUILD TWO OR THREE SMALL COTTAGES. THERE WAS A BIG PILE OF BROKEN BRICKS AND MORTAR LYING AGAINST ONE SIDE OF THE BARN; AND ANOTHER LARGE PILE OF BOWLDERS, OR FIELD STONES, NEAR THE FENCE. "THESE," FRED SAID, "WILL BE FINE TO BUILD A LITTLE LANDING PLACE OR PIER FOR THE BOAT. THE BROKEN BRICKS AND HARD MORTAR WILL MAKE GRAND STUFF FOR THE FOUNDATION OF the cement pathway." THERE WERE ALSO TWO OR THREE SMALL BUILDINGS ON THE PLACE. ONE HAD BEEN USED FOR A POULTRY HOUSE, ANOTHER FOR A TOOL HOUSE, AND A THIRD SEEMED TO HAVE BEEN A SORT OF CATTLE SHED. MR. GREGG SUGGESTED THEIR REMOVAL, OF WHICH ALL approved. THERE WERE QUITE A NUMBER OF GOOD-SIZED TREES ON THE GROUNDS, AND THESE RENDERED IT A LITTLE DIFFICULT TO SET OUT A STRAIGHT LINE TO THE RIVER FOR THE CEMENT WALK, WITHOUT CUTTING DOWN SEVERAL, WHICH COULD NOT BE CONSIDERED. THERE WAS ONE DIRECTION, HOWEVER, THAT WOULD ADMIT OF A WALK, ABOUT FOUR FEET WIDE, BUT THERE WERE SOME BIG ROCKS OR BOWLDERS IN THE way, that would have to be removed before a straight path could be made. Still it was decided to put it there. "THE ROCKS," SAID THE FATHER, "CAN BE REMOVED BY BLASTING, BY LIFTING THEM OUT OF THEIR BEDS AND ROLLING THEM ASIDE, OR moving them down to the river, where they will form a good protection against both current and ice." "I think they can be moved," said Fred, "if I can get levers and rollers; and they will make fine breakwater stones." JESSIE FOUND TWO SUITABLE TREES, UPON WHICH FRED PROMISED TO PUT UP A STRONG ROPE SWING, AS SOON AS THE PLACE COULD BE cleaned up and made tidy. "NOW, FRED," SAID THE FATHER, "THIS CEMENT WALK SHOULD BE COMMENCED AT ONCE, SO THAT IT WILL BE DRY AND HARD BEFORE YOU GO ON WITH OTHER WORK. I WILL EMPLOY A LABOURING MAN TO HELP YOU, ONE WHO WILL DO THE HEAVY WORK, AS I DO NOT WANT YOU TO OVER-EXERT YOURSELF. YOU HAVE A NUMBER OF TOOLS NOW IN THE SHED, AND, WHEN I COME HOME FROM THE OFFICE THIS EVENING, WE WILL MAKE OUT A LIST OF THE OTHER TOOLS AND MATERIALS YOU WILL REQUIRE TO FINISH THE INTENDED WORK. IN THE MEANTIME YOU AND GEORGE CAN BE MAKING A NUMBER OF WOODEN STAKES, ABOUT EIGHTEEN INCHES LONG AND TWO INCHES SQUARE. POINT THEM SHARPLY AT ONE END SO THAT THEY MAY BE DRIVEN INTO THE GROUND THEIR WHOLE LENGTH. YOU WILL REQUIRE THIRTY OR FORTY OF THESE. AFTER GETTING THEM, TAKE A CLOTHES LINE, OLD HALYARD, OR ANY ROPE OR HEAVY STRING YOUR MOTHER CAN FIND FOR YOU, AND STRETCH IT FROM THE HOUSE DOWN TO THE RIVER, AT THE POINT WE DECIDED UPON. DRIVE IN A STAKE NEAR THE RIVER, TIE ONE END OF THE ROPE TO IT, PULL TIGHTLY, AND STRETCH THE ROPE FROM THE RIVER TO THE HOUSE. IT WILL THEN SHOW YOU WHERE ONE EDGE OF THE WALK IS TO BE. AFTER THAT IS DONE, GET ANOTHER ROPE OR STRING AND, STARTING FROM THE HOUSE END OF THE WALK, MEASURE OFF FOUR FEET FOR THE PROPOSED WIDTH. DRIVE IN A STAKE AT THAT POINT, AND TIE ONE END OF THE SECOND ROPE TO IT; THEN GO TOWARD THE RIVER WITH THE OTHER END, MAKING THE ROPE EXTEND THE WHOLE LENGTH OF THE PATH AND DRIVE IN ANOTHER STAKE WHICH MUST BE FOUR FEET FROM THE FIRST ROPE. TO THIS STAKE TIE THE END OF THE ROPE AND MAKE IT TIGHT. BE SURE TO HAVE THE TWO ROPES EXACTLY FOUR FEET APART AT EACH END, AS WELL AS ALONG THE WHOLE LENGTH. YOU WILL FIND IT TO YOUR advantage to get a straight strip of wood, say, one or two inches thick both ways, and cut it exactly four feet long. It can THEN BE USED AS A MEASURING STICK OR GAUGE, FOR THE DISTANCE BETWEEN THE ROPES, WHICH IS TO BE THE WIDTH OF THE WALK, and by using it you will have a parallel and uniform path from start to finish." MR. GREGG HAD PASSED AN EXAMINATION IN THE MASSACHUSETTS SCHOOL OF TECHNOLOGY, AND HAD WON A POSITION AS CIVIL ENGINEER IN NEW YORK WHICH LATER HE ABANDONED FOR THE PROFESSION OF LAW; HENCE HIS KNOWLEDGE OF PRACTICAL MECHANICS and engineering. AFTER JESSIE AND GEORGE HAD GONE TO SCHOOL, FRED STARTED ON HIS NEW UNDERTAKING WITH ENTHUSIASM. HE FOUND QUITE A NUMBER OF PIECES OF WOOD, OUT OF WHICH HE MADE OVER FORTY STAKES, AND POINTED THEM NICELY WITH THE LARGE HATCHET HE ALWAYS KEPT SHARP AND IN GOOD ORDER. BY TYING SEVERAL PIECES TOGETHER, IT DID NOT TAKE HIM LONG TO FIND CORD ENOUGH TO SET OUT THE WHOLE WALK. AN OLD HALYARD THAT HAD BEEN TAKEN FROM THE FLAG POLE AND REPLACED BY A NEW ONE ANSWERED THE PURPOSE ADMIRABLY. DRIVING A STAKE INTO THE GROUND, NEAR THE HOUSE, HE TIED ONE END OF HIS CORD TO THAT, AND STRETCHED IT DOWN TO THE RIVER BANK TO THE POINT CHOSEN FOR THE END OF THE WALK, WHERE ANOTHER STAKE WAS DRIVEN IN AND THE CORD TIED TO IT. THE LONG STRETCH BETWEEN THE TWO STAKES WOULD NOT ALLOW THE CORD TO BE TIGHT ENOUGH TO MAKE A STRAIGHT LINE BETWEEN THE TWO POINTS, BUT FRED LEFT IT AS IT WAS, TO BE ADJUSTED WHEN HIS FATHER CAME. WITH HIS ROD HE MEASURED OFF FOUR FEET FROM THE FIRST STAKE, ACROSS THE INTENDED PATH, AND DROVE IN ANOTHER STAKE TO WHICH HE ATTACHED ANOTHER CORD. THEN GOING DOWN TO THE RIVER HE MEASURED OFF THE WIDTH OF THE WALK FROM THE LONG CORD, AND DROVE IN ANOTHER STAKE. HE WAS NOW READY TO HAVE HIS FATHER EXAMINE THE WORK HE HAD DONE, AND TO MAKE SUGGESTIONS OR CHANGES IF SUCH WERE deemed necessary. Jessie and George arrived home from school, having run most of the way, "to help Fred make the walk," and were quite disappointed to be told there was nothing they could do until the work was further advanced. "WE MIGHT, PERHAPS, COMMENCE TAKING DOWN THE OLD BUILDINGS," SAID FRED, "AND PILE THE LUMBER WHERE IT WILL BE SNUG and dry." "ALL RIGHT," SAID GEORGE; SO THE THREE OF THEM WENT OVER TO THE POULTRY HOUSE AND FRED BEGAN BY TAKING OUT THE TWO OR THREE SMALL WINDOWS, AND REMOVING THE DOORS BY UNSCREWING THE HINGES. GEORGE'S DESIRE TO PULL, TEAR, AND SMASH THE OLD MATERIAL WAS HELD IN CHECK BY FRED, WHO ADVISED HIM TO BE CAREFUL, AND NOT BREAK OR DESTROY ANYTHING THAT COULD BE [8] [9] [10] [11] [12] USED. AFTER THE DOORS HAD BEEN TAKEN OFF AND LAID NICELY AWAY—"TO BE USED ON THE BOAT HOUSE"—AND THE WINDOWS AND FRAMES PLACED IN A DRY SPOT, FRED BEGAN TO REMOVE THE OLD SIDING, OR CLAPBOARDS. HE FOUND THIS A RATHER DIFFICULT JOB, AS THEY WERE NAILED ON WITH OLD-FASHIONED WROUGHT-IRON NAILS WHICH COULD NOT READILY BE DRAWN, AND, IN TRYING TO GET THE BOARDS LOOSE, THE ENDS KEPT BREAKING AND SPLITTING; SO HE STOPPED, WENT INSIDE THE BUILDING, AND TOOK OFF THE LINING THERE; this also was a little difficult to do, but, as the boards were an inch thick, he did not split many of them. HE THEN SAWED OFF THE BOARDS ALONGSIDE THE STUDS, ON THE CORNERS, AND AT THE DOORWAYS TO RELIEVE THE SIDING AT THE ENDS, AND GIVE HIM A GOOD CHANCE TO WEDGE OFF THE BOARDS WHEREVER THEY WERE NAILED. WITH THE HELP OF GEORGE, HE SUCCEEDED IN GETTING MOST OF THEM LOOSE WITHOUT SERIOUS DAMAGE. OF COURSE, HE HAD TO BEGIN TEARING THE BOARDS OFF AT the top of the wall, as they lapped over each other like the scales of a fish. MR. GREGG ARRIVED, WENT OVER THE GROUND, AND WAS WELL PLEASED WITH THE RESULTS OF FRED'S DAY'S WORK. HE ASSISTED IN STRAIGHTENING THE LONG CORDS, AND MADE A NUMBER OF SUGGESTIONS FOR THE BOYS TO FOLLOW. HE HAD A STRONG-LOOKING MAN WITH HIM, WHO HE TOLD FRED WAS TO HELP HIM. HE WAS AN ITALIAN, NAMED NICOLO, CALLED "NICK" FOR SHORT, A KINDLY FELLOW, WHO COULD SPEAK ENGLISH FAIRLY, FOR HE HAD BEEN EMPLOYED IN NEWARK, AS A HANDY LABOURING MAN FOR YEARS. HE, FRED, AND GEORGE SOON BECAME GOOD COMPANIONS, AND EVEN JESSIE, THOUGH A LITTLE SHY AT FIRST, SOON BECAME QUITE FRIENDLY TOWARD HIM. WHEN IT WAS EXPLAINED WHAT WAS WANTED OF HIM, HE WAS QUITE SATISFIED, AND AGREED TO BEGIN WORK IN THE morning. NEXT DAY FRED AND GEORGE WERE AT WORK BEFORE THEIR FATHER WAS OUT, AND SOON NICK ARRIVED, BRINGING A SPADE, A CROWBAR, AND A PICK. HE WAS IMMEDIATELY SET TO WORK BY FRED, DIGGING A SHALLOW TRENCH FOR THE PATHWAY, A LITTLE OVER four feet wide and about eight inches deep. The stretched cord and the four-foot rod were the guides. Fig. 1. Section of sidewalk THERE WERE A NUMBER OF ROCKS TO BE REMOVED FROM THE TRENCH, ONE OF THEM NEAR THE RIVER BANK WEIGHING OVER A TON. These were left to be removed later. Their father, on coming out, was glad to see them all at work; he showed Fred and NICK HOW TO PREPARE THE EDGES OF THE TRENCH BY PUTTING PLANKS ALONG THEM, AS SHOWN IN FIG. 1. THE BOARDS, ABOUT twelve inches wide, and from twelve to sixteen feet long, had been taken from the old barn. AFTER BREAKFAST FRED WORKED ALONG WITH HIS MAN, AND GOT THE TRENCH WELL CLEANED OUT, EXCEPT FOR A FEW OF THE LARGER ROCKS. THE SMALLER BOWLDERS WERE WHEELED DOWN TO THE RIVER AND ROLLED OVER THE BANK TO THE WATER'S EDGE. NEAR ONE SIDE OF THE WALK GREW A LARGE TREE, WHOSE MAIN ROOT RAN UNDER THE PROPOSED PATH. MR. GREGG HAD NOTICED THIS IN THE MORNING AND HAD TOLD FRED TO SEE THAT THE ROOT WAS CUT OFF CLOSE TO THE LINE ON BOTH SIDES AND PULLED OUT ALTOGETHER. "IF IT ISN'T CUT OFF, IT WILL GROW LARGER, LIFT UP THE CEMENT FLAGS, AND PERHAPS BREAK THEM." FRED SAW THE FORCE OF THIS, SO HAD THE root cut off and taken out. The operation would not kill the tree, though it might do it some injury. NOW CAME THE PROCESS OF TAKING OUT THE BIG STONES, AND A LEVER, TEN OR TWELVE FEET LONG, WAS BROUGHT FROM THE BARN, IN THE SHAPE OF A RED CEDAR POLE, FIVE OR SIX INCHES IN DIAMETER AT THE LARGER END. NICK TOOK AN AXE AND CHOPPED THE BIG END A LITTLE FLAT ON TWO SIDES, SO THAT IT COULD BE SHOVED UNDER THE STONE. A FLAT PLANK WAS NEXT LAID BEHIND THE STONE ON THE GROUND, ON WHICH A FULCRUM WAS TO BE PLACED, IN ORDER TO GET WHAT IS TERMED BY WORKMEN A "PURCHASE." ON THE SIDE OF THE STONE NEXT TO THE RIVER, THREE PLANKS TAKEN FROM THE FLOOR OF THE BARN WERE LAID DOWN FLAT AT THE BOTTOM OF THE TRENCH. THREE OTHER PLANKS WERE LAID ON THE TOP OF THE FIRST LAYER, THUS MAKING A BED IN THE TRENCH, TWO PLANKS IN THICKNESS, ON WHICH THE BIG STONE WAS TO BE ROLLED. A FULCRUM, CONSISTING OF AN OLD FENCE POST, WAS LAID UPON THE PLANK, AND FORCED UP AS CLOSE TO THE STONE AS POSSIBLE. EVERYTHING WAS NOW READY FOR LIFTING THE BOWLDER OUT OF THE BED, WHERE it had lain perhaps for thousands of years. AS HAD BEEN ARRANGED, THE WORK AT THIS STAGE WAS SUSPENDED, AND OTHER WORK GONE ON WITH, UNTIL MR. GREGG MADE HIS APPEARANCE. UPON HIS ARRIVAL ALL HANDS WENT TO THE STONE, JESSIE INCLUDED. HAVING APPROVED WHAT HAD BEEN DONE, THE FATHER SUGGESTED THAT ROLLERS BE PLACED BETWEEN THE TWO THICKNESSES OF PLANK TO INCREASE THE EASE OF MOVING THE STONE TO THE RIVER WHEN IT WAS STARTED. FRED AND NICK WENT TO THE BARN, AND AMONG A BIG PILE OF OLD PLANKS, BOARDS, AND TIMBER FOUND EIGHT OR TEN OLD FENCE POSTS, SIX OR EIGHT INCHES IN DIAMETER, AND LONG ENOUGH TO MAKE TWO ROLLERS, EACH THREE FEET LONG, WHEN CUT IN TWO. THESE WERE QUICKLY STRIPPED OF BARK BY GEORGE AND JESSIE, WHILE NICK AND FRED, WITH AXE AND HATCHET, SOON HAD A NUMBER OF THEM ROUND ENOUGH TO SERVE AS ROLLERS. THE FATHER THEN DIRECTED THAT THE ENDS NEAREST THE RIVER, OF THE TOP LAYER OF PLANKS, BE RAISED UP, AND ONE OF THE ROLLERS PLACED BETWEEN THE TWO LAYERS OF PLANK NEAR THE STONE, WHILE THE ENDS OF PLANKS NEAREST THE STONE SHOULD BE LEFT RESTING ON THE BOTTOM ONES. ANOTHER ROLLER WAS PLACED NEARER THE RIVER END OF THE PLANKS, AND ALL WAS MADE, AS SHOWN AT FIG. 2—WHERE FULCRUM, LEVER, STONE, PLANKS, AND rollers may be seen. Fig. 2. Raising rock with lever ALL WAS NOW READY; THE LEVER WAS ADJUSTED IN PLACE UNDER THE STONE AND ON THE FULCRUM. MR. GREGG, NICK, AND THE CHILDREN WERE GATHERED ABOUT THE LEVER, EACH ONE PUSHING DOWN, AND THE STONE BEGAN TO MOVE, AS THE TOP END OF THE LEVER CAME DOWN, MUCH TO THE DELIGHT OF JESSIE AND GEORGE, WHO KEPT SHOUTING, "THERE SHE GOES! UP SHE GOES!" FINALLY [13] [14] [15] [16] [17] THE GREAT STONE TURNED OVER ON THE PLANK, AND WAS MOVED TO NEAR THE CENTRE. NOW CAME THE LABOUR OF GETTING THE MONSTER DOWN TO THE BANK. THIS WAS MADE EASIER BY RAISING THE ENDS OF THE UPPER PLANKS UNDER THE STONE AND inserting ANOTHER ROLLER, FIVE OR SIX FEET FROM THE END. THE PLANKS HOLDING THE STONE WERE NOW RESTING ON ROLLERS, AS SEEN IN FIG. 3, AND IT WAS FOUND EASY TO MOVE, BUT IN ORDER TO GET IT TO THE BANK OF THE RIVER THE "RUNWAY," OR LOWER PLANKS, HAD TO BE LAID DOWN THAT DISTANCE; THIS WOULD TAKE TOO MANY PLANKS, SO IT WAS DECIDED TO LAY ONLY A SECOND LENGTH ON THE GROUND, AND THEN WHEN THE LOAD HAD TRAVELLED TO THIS LENGTH, THE PLANK BEHIND THE STONE SHOULD BE CARRIED FORWARD AND LAID DOWN AGAIN. THIS WAS CONTINUED UNTIL THE LOAD WAS SLID INTO THE WATER. MR. GREGG CALLED THE CHILDREN AND TOLD THEM TO PUSH against the stone, and they all were filled with wonder to see this great stone move along so easily on the rollers. Fig. 3. Moving rock on rollers FRED AND NICK GOT MORE ROLLERS TO PUT BETWEEN THE PLANKS AS THE STONE WAS PUSHED FORWARD, FOR, OF COURSE, THESE WERE CONTINUALLY COMING OUT AT THE REAR END OF THE LOADED PLANKS. THE ROLLERS HAD ALSO TO BE WATCHED AND KEPT SQUARE ACROSS the plank or they would slide, making it hard to move the load. WHEN THE RIVER BANK WAS REACHED, FRED AND NICK MADE A ROUGH SLIDE OF OLD TIMBER DOWN TO ITS SIDE FROM THE TRENCH. GETTING THE LEVER PROPERLY ADJUSTED UNDER THE PLANKS AND STONE, THE LATTER WAS TURNED OVER ON THE SLIDE, WHEN IT PLUNGED INTO THE RIVER WITH A GREAT SPLASH, CAUSING THE WATER TO FLY AND SPRINKLE EACH ONE OF THE WORKERS, MUCH TO THE DELIGHT OF George, who thought it fine fun to see his father, Fred, and Nick get a wetting. IT WAS DECIDED THAT THE STONE AS IT LAY IN THE WATER SHOULD FORM THE END OF THE PIER FOR THE BOAT, AS IT WAS NICELY SITUATED and the proper distance out, being about a foot out of the water at high tide. The other stones were easily removed from THE TRENCH BY FRED AND HIS MAN, AND WERE EITHER ROLLED OR WHEELED DOWN TO THE RIVER, WHERE NICK BUILT THEM AS WELL AS HE COULD ON BOTH SIDES OF THE BIG ROCK, LEAVING A HOLLOW SPACE BETWEEN THE WALLS, TO BE FILLED IN AFTERWARD WITH SMALL stones, mortar, and broken bricks, for the making of a good, strong boat pier. MR. GREGG THEN TOOK OUT HIS NOTE-BOOK AND PENCIL, AND FIGURED OUT THE QUANTITY OF CEMENT, SAND, AND GRAVEL REQUIRED TO COMPLETE THE CEMENT WORK. HE FOUND THERE WAS GOOD SAND, CLEAN AND SHARP, ON ONE CORNER OF THE NEW LOT. A BIG PILE OF GRAVEL AND BROKEN STONES OUT ON THE STREET HAD BEEN LEFT OVER FROM THE BUILDING OF A TWO-STORY CONCRETE HOUSE NEARBY, so he concluded to buy it, if not too dear. MEASURING THE TRENCH, HE FOUND IT TO BE 300 FEET LONG, BY 4 FEET WIDE, MAKING A SURFACE OF 1,200 FEET TO BE LAID WITH CEMENT, CONCRETE, AND GRAVEL, OR BROKEN STONES. HE CALCULATED THAT EVERY 100 SUPERFICIAL FEET OF THE CONCRETE WALK WOULD REQUIRE ABOUT A BARREL AND A THIRD OF PORTLAND CEMENT; AND THAT THE TOP DRESSING OF CEMENT AND SAND, OR FINE CRUSHED STONE, REQUIRED ANOTHER THIRD OF A BARREL; WHICH TOTALED UP TO 20 BARRELS, ALL TOLD. THE CONCRETE TO BE USED WAS TO BE PROPORTIONED AS FOLLOWS: ONE PART OF CEMENT, TWO PARTS OF GOOD, CLEAN SAND, AND FIVE PARTS OF GRAVEL, OR BROKEN STONES, WHICH SHOULD BE SMALL ENOUGH TO PASS THROUGH A RING HAVING A DIAMETER OF NOT MORE THAN TWO INCHES. THIS MASS SHOULD BE WELL MIXED, DRY, ON A WOODEN FLOOR OR MOVABLE PLATFORM, AND THEN WETTED JUST ENOUGH TO HAVE STONES, SAND, AND CEMENT, WELL MOISTENED. ALL SHOULD BE AGAIN MIXED BEFORE BEING PLACED IN THE TRENCH, AND IT SHOULD NOT BE THROWN IN place, but shovelled in gently. MR. GREGG ORDERED THE CEMENT BY TELEPHONE, TO BE DELIVERED AT ONCE, EITHER IN BARRELS OR BAGS; AND HE GOT INTO COMMUNICATION WITH THE OWNER OF THE GRAVEL, AND BOUGHT THE WHOLE PILE. HE THEN ENGAGED A TEAM OF HORSES, WAGON, AND DRIVER, TO COMMENCE WORK THE NEXT DAY. BY THIS TIME NICK HAD GONE HOME, AND THE CHILDREN CAME RUSHING INTO THE house, anxious to tell their mother all the work they had done that day. THE KEEN APPETITES OF THE YOUNGER FOLKS GAVE POSITIVE PROOF OF THEIR HAVING EARNED THEIR SUPPER, BY ACTUAL WORK, AND, WHEN THE MEAL WAS OVER, THE FATHER INVITED JESSIE AND THE BOYS INTO HIS LITTLE ROOM. GEORGE WAS ASKED TO TAKE WITH HIM his portable blackboard, some chalk, and a ruler, and all marched into their father's den. "NOW," SAID MR. GREGG, "I HAVE OFTEN TOLD YOU I WOULD EXPLAIN TO YOU SOME THINGS ABOUT THE MECHANICAL POWERS, AND THIS SEEMS TO BE THE MOST APPROPRIATE TIME TO BEGIN, AS YOU HAVE FRESH IN YOUR MINDS THE APPLICATION OF THE LEVER AS WE USED IT TO-DAY IN RAISING AND MOVING THE BIG ROCK. I AM GLAD TO SEE THAT FRED GRASPED THE IDEA SO READILY, FOR THAT encourages me to let him use his own judgment while doing this job. "THE LEVER IS KNOWN TO ACCOMPLISHED MECHANICS, AS 'THE FIRST MECHANICAL POWER', AND ARCHIMEDES SAID OF IT, IF HE ONLY had one long and strong enough, together with a suitable fulcrum, he could, alone, lift the earth from its place. "THIS ARCHIMEDES WAS A CELEBRATED GREEK PHILOSOPHER AND MATHEMATICIAN, WHO LIVED FROM ABOUT 287 TO 212 B. C. THE DISCOVERY OF THE LAW OF SPECIFIC GRAVITY, WHICH I WILL SOME DAY TELL YOU ABOUT, IS ATTRIBUTED TO HIM. I THINK GEORGE CAN TELL YOU SOMETHING ABOUT THIS GREAT MAN, AS I SAW HIM AND JESSIE THE OTHER DAY READING PLUTARCH'S 'LIVES,' IN WHICH HE IS mentioned. Fig. 4. Principle of lever and fulcrum "A LEVER MAY BE FORMED OF ANY STRONG, STIFF MATERIAL, WOOD, IRON, STEEL, OR SIMILAR STUFF, AND IT MAY BE OF ANY LENGTH, OR [18] [19] [20] [21] [22] Fig. 5. Lever as a mechanical power Fig. 6. Double lever as scales DIMENSIONS, ACCORDING TO THE PURPOSE FOR WHICH IT IS TO BE USED. IN THEORY, IT IS SUPPOSED TO HAVE NO WEIGHT, AND IS SIMPLY FIGURED AS A STRAIGHT LINE HAVING NEITHER BREADTH NOR THICKNESS. IN PRACTICE, HOWEVER, A LEVER MAY BE A HANDSPIKE, A PRY, A CROWBAR, A FIRE POKER, A WINDLASS BAR, OR ANY OTHER APPLIANCE OR INSTRUMENT THAT CAN BE USED FOR PRYING. WHILE WE MAY NOT KNOW THE PROPER NAME OF THE LITTLE STEEL TOOL THE DENTIST EMPLOYS WHEN PREPARING ONE'S TEETH TO RECEIVE THE FILLING, BY CLEANING OUT THE CAVITIES, WE ARE SAFE IN CALLING IT A SMALL LEVER. WHEN YOUR MOTHER STIRS THE FIRE IN THE GRATE, SHE MAKES A LEVER OF THE POKER, AND BARS OF THE FIREPLACE BECOME FULCRUMS. THE FULCRUM IS THE FIXED POINT ON WHICH THE LEVER RESTS WHEN IN USE. THE FORCE APPLIED IS CALLED THE POWER AND THE OBJECT TO BE ACTED UPON IS CALLED THE WEIGHT. THE SPACES FROM THE POWER AND THE WEIGHT, RESPECTIVELY, TO THE FULCRUM, ARE CALLED THE ARMS OF THE LEVER. THERE ARE THREE DIFFERENT WAYS OF USING THE LEVER, ACCORDING TO THE RELATIVE POSITIONS OF POWER, WEIGHT, AND FULCRUM. THIS ROUGH SKETCH I AM DRAWING ON THE BLACKBOARD ( Fig. 4) SHOWS THE LEVER BEING USED TO RAISE ONE END OF A HEAVY STONE. SUPPOSE W IS A BIG ROCK, C WILL BE THE FULCRUM, B THE END OF THE LEVER UNDER THE STONE, AND O THE POWER. THE WEIGHT THROWN ON THE LEVER BY THE MAN AT O, RAISES THE STONE SO THAT IT CAN BE BLOCKED UP, THE LEVER AND FULCRUM ARRANGED FOR ANOTHER LIFT, AND THE PROCESS REPEATED. THIS CAN BE CONTINUED UNTIL THE STONE IS RAISED TO THE HEIGHT REQUIRED, OR UNTIL IT IS TURNED OVER. THIS method applies to the raising of any sort of weight, engine, boiler, heater, etc. "IN THIS SKETCH THE DISTANCE FROM B TO C SHOWS THE SHORT ARM OF THE LEVER, AND THE DISTANCE FROM C TO O SHOWS THE length of the long arm. "A LEVER, USED IN THIS WAY, IS CALLED A LEVER OF THE FIRST KIND, BECAUSE OF ITS SIMPLICITY AND EASY ADAPTATION TO MANY PURPOSES. I SAW GEORGE DIGGING IN THE GARDEN THE OTHER DAY, MAKING A FLOWER BED FOR HIS MOTHER. THE SPADE HE USED FORMED AN EXCELLENT LEVER. HE FORCED IT INTO THE GROUND TO ITS FULL DEPTH, PRIED THE HANDLE TOWARD HIM, AND BROKE LOOSE THE SOIL, AFTER WHICH HE TURNED OVER THE EARTH IN THE BED. NOW, IN THIS CASE, THE TOP OF THE BLADE OR FOOT-PLATE OF THE SPADE, RESTED ON THE HARD GROUND, WHICH WAS THE FULCRUM; THE SOIL DUG UP WAS THE WEIGHT, AND GEORGE'S HAND AT THE TOP OF THE SPADE HANDLE, FURNISHED THE POWER. I am sure you all understand the working of a lever of this kind, but I will give you another illustration. "HERE'S ANOTHER SKETCH ( FIG. 5), IN WHICH A,B,C, TOGETHER SHOW THE LEVER, ALSO THE POWER A, THE FULCRUM B, AND THE WEIGHT C. IF I SHOULD PLACE THE FULCRUM B SO THAT IT WOULD BE IN THE MIDDLE BETWEEN THE ENDS A C, THERE WOULD BE WHAT IS TERMED AN EQUILIBRIUM BETWEEN THE WEIGHT AND THE POWER, AND IF THEY ARE EQUAL THERE WILL BE A PERFECT BALANCE MAINTAINED. IT IS ON THIS PRINCIPLE THAT SCALES FOR DRUGGISTS ARE MADE, THE LEVER BEING SUSPENDED IN THE CENTRE OF ITS LENGTH, AS I SHOW IN THE SKETCH ( FIG. 6). THESE SCALES ARE VERY NICELY ADJUSTED, AND THE CHAINS AND RECEIVERS ARE MADE AS NEARLY ALIKE IN WEIGHT AS POSSIBLE. THE ARMS OF THE LEVER BEING OF EQUAL LENGTH FROM THE CENTRE, OR PIVOT, PERMIT THE LEVER TO STAND IN A PERFECTLY HORIZONTAL POSITION, UNLESS DISTURBED BY HAVING A WEIGHT PLACED IN EITHER ONE OR OTHER OF THE RECEIVERS. IN THIS CASE, THE PIVOTED POINT P IS THE FULCRUM, AND THE TWO POINTS O AND X MAY BE TAKEN AS THE POWER AND THE WEIGHT. IF ONE POUND IS PLACED IN THE RECEIVER AT O, IT WILL TIP THE SCALE DOWN, AND THAT WILL BECOME THE WEIGHT, WHILE ANY COMMODITY PLACED IN THE RECEIVER AT X, UNTIL THE LEVER IS AGAIN BROUGHT LEVEL, OR HORIZONTAL, MAY BE CALLED THE POWER. AS ANOTHER ILLUSTRATION I'LL TELL YOU OF SOMETHING THAT TOOK PLACE THE OTHER DAY. IN THE VACANT LOT ARE SEVERAL PILES OF BRICKS, STONES, AND PLANKS. GEORGE, SEEING THIS, TOOK ONE OF THE PLANKS AND THREW IT ACROSS SEVERAL OTHERS, MAKING A 'TEETER TAUTER,' OR, AS SOME CHILDREN CALL IT, A 'SEESAW.' HE BALANCED THE PLANK NICELY, AND THEN INVITED JESSIE AND HER COUSIN TO SIT ON IT, ONE AT EACH END. THE TWO GIRLS WERE ABOUT THE SAME WEIGHT, AND GEORGE HELD THE PLANK UNTIL BOTH WERE SEATED. IT REMAINED LEVEL AND BALANCED, UNTIL GEORGE GOT ON THE TOP OF IT, AND STOOD ON THE CENTRE OF ITS LENGTH, PLACING HIS FEET SO THAT ONE WAS ON ONE SIDE OF THE CENTRE, OR FULCRUM, AND THE OTHER ON THE OTHER. BY CAUSING HIS WEIGHT TO REST ON HIS RIGHT FOOT, THE RIGHT END OF THE PLANK WOULD DIP DOWNWARD; THEN BY THROWING HIS WEIGHT ON HIS LEFT FOOT, THE MOVEMENT OF THE PLANK WOULD BE REVERSED, AND THE MOTION CONTINUED UNTIL GEORGE CEASED TO EXERT ANY EXTRA PRESSURE ON EITHER OF HIS FEET. WHAT DO YOU CALL THE BOY OR GIRL WHO stands on the plank?" "Sometimes," said Jessie "we call him a 'candlestick' and sometimes 'the balancer'." "THIS TEETER TAUTER AND THE EXPLANATION OF THE DRUGGIST SCALES," SAID THE FATHER, "SHOW YOU THAT MANY OF OUR CONVENIENCES ARE DUE TO THE LEVER IN ONE WAY OR ANOTHER. THESE ARE BUT A FEW OF THE THOUSANDS OF INSTANCES I COULD NAME. TAKE A NUT- CRACKER, FOR INSTANCE. THERE WE HAVE A SORT OF DOUBLE LEVER, THE JOINT BEING THE FULCRUM, THE NUT THE WEIGHT, AND THE TWO HANDLES THE COMBINED POWER OR LEVER. BY PRESSING THE HANDLES OR LEVERS, WE CRACK THE NUT OR OVERCOME THE WEIGHT, BY CRUSHING IT. WE OWE MANY OF OUR AMUSEMENTS TO THE LEVER IN ONE FORM OR ANOTHER. EVEN OUR PIANOS WOULD BE IMPOSSIBLE WERE IT NOT FOR THE COMBINATION OF LEVERS IN THE ADJUSTMENT OF THE KEYS. MACHINERY AND ALL KINDS OF MOVING INSTRUMENTS, INCLUDING WATCHES, CLOCKS, AND OTHER FINE MECHANISM, COULD NOT BE PERFECTED WITHOUT THE LEVER. THE COMMON EVERY-DAY WHEELBARROW IS A GOOD ILLUSTRATION OF THE USE OF THE LEVER COMBINED WITH THE WHEEL. GEORGE FILLS UP HIS BARROW WITH STONES OR OTHER MATERIALS THAT WEIGH TWO OR THREE TIMES THE AMOUNT HE COULD LIFT EASILY. YET HE GETS AWAY WITH THE LOAD, APPARENTLY WITH VERY LITTLE TROUBLE. THE HANDLES FORM THE LEVER OR POWER, THE WHEEL THE FULCRUM, AND THE STONES THE WEIGHT. GEORGE RAISES THE HANDLES, AND THROWS THE GREATER PART OF THE WEIGHT ON THE FULCRUM, WHICH IS THE WHEEL, AND THIS latter, acting as a roller, is easily moved around its own axle, thus enabling George to move his threefold load with ease. "THIS EXAMPLE SHOWS YOU HOW, BY A SIMPLE COMBINATION OF MECHANICAL DEVICES, LABOUR MAY BE REDUCED. THE ROLLER IS related to the wheel and axle class—another of the mechanical powers. "IN YOUR BICYCLES YOU HAVE A FINE ILLUSTRATION OF THE APPLICATION OF THE ROLLER PRINCIPLE, IN THE BALL-BEARINGS. THE LITTLE ROUND BALLS, OVER WHICH THE AXLE OF THE WHEEL RUNS, ARE SIMPLY ROLLERS ROUNDED IN EVERY DIRECTION, AND PLACED THERE TO DESTROY [23] [24] [25] [26] [27] [28] friction, which they do almost entirely. "ANOTHER EXCELLENT ILLUSTRATION OF THE USE OF THE ROLLER IS SEEN IN THE HANGING OF THE GRINDSTONE WE HAVE IN OUR BACK SHED. THE AXLE PASSING THROUGH THE STONE RESTS ON TWO PAIRS OF WHEELS OR ROLLERS, ONE PAIR AT EACH SIDE OF THE STONE. IF YOU TURN THE STONE ON ITS AXIS, YOU WILL NOTICE THE WHEELS TURN ALSO, AND THE EFFORT REQUIRED TO TURN THE STONE IS HARDLY NOTICEABLE. IF THE GRINDSTONE WERE WELL BALANCED AND TRUE, AND THE LITTLE WHEELS THE SAME, SO THAT THEY COULD BE RUN WITHOUT FRICTION ON THEIR BEARINGS, THE STONE, BY GIVING IT ONE GOOD TURN WITH THE HAND, WOULD KEEP REVOLVING A VERY LONG TIME. SO YOU SEE how much we are indebted to the mechanical powers for our present state of civilization." NEXT MORNING BEING SATURDAY, GEORGE WAS UP EARLY, PUT ON A PAIR OF OVERALLS HIS MOTHER HAD BOUGHT, AND, WHEN BREAKFAST WAS OVER, ALL BUT THE MOTHER WENT OUT TO THE NEW PROPERTY. THEY FOUND NICK HELPING A TEAMSTER TO UNLOAD GRAVEL, ALSO A LOAD OF CEMENT, WHICH WAS PLACED IN A DRY AND CONVENIENT PLACE, FOR ONCE DAMP OR WET IN THE LEAST IT BECOMES OF LITTLE USE, UNLESS WORKED UP IMMEDIATELY. GEORGE WAS FULL OF GLEE. HE GOT HIS WHEELBARROW AND WANTED TO COMMENCE WORK WITHOUT DELAY. THE FATHER TOOK FRED AND NICK TO THE TRENCH AND EXPLAINED WHAT WAS TO BE DONE AND THE WAY TO DO IT. "THE TRENCH IS NOW EIGHT INCHES DEEP," HE SAID, "AND YOU MUST WHEEL GRAVEL, BROKEN BRICKS, HARD MORTAR, OR CINDERS INTO IT SO THAT THERE WILL BE ABOUT FIVE INCHES OF IT IN THE TRENCH FROM ONE END TO THE OTHER. PUT ALL THE LARGER STONES AT THE BOTTOM, BUT BEFORE THROWING IN ANY, TAMP OR POUND THE GROUND AT THE BOTTOM OF THE TRENCH UNTIL IT IS SOLID AND HARD, MAKING A GOOD BOTTOM FOR THE STONES TO REST ON, AND ENSURING THE WALK FROM SETTLING OR SINKING IN SPOTS. WHERE THE BIG ROOT AND ROCKS ARE TAKEN OUT, THE HOLES MUST BE FILLED UP LEVEL, AND TAMPED SOLID. RAKE OFF THE LARGEST OF THE GRAVEL, AND LET GEORGE WHEEL AS MUCH OF IT AS HE CAN, AND DUMP IT IN THE TRENCH, WHILE NICK OR YOU WHEEL IN THE BALANCE. FINISH THE TOP OF THE GRAVEL OFF WITH SMALLER SIZED STONES, AND AFTER YOU HAVE FILLED IN ABOUT FIVE INCHES, THROW WATER ON THE WHOLE WITH THE GARDEN HOSE UNTIL QUITE WET, AND THEN POUND THE GRAVEL DOWN UNTIL IT IS COMPACT AND FIRM. This bed forms a good foundation for the concrete which must be laid on it about four inches thick, and well tamped. "AFTER YOU HAVE RAKED OFF THE LARGER GRAVEL, TAKE A WIRE SIEVE, WITH MESHES NOT LARGER THAN FOUR TO THE INCH, AND SIFT THE FINER GRAVEL OUT, TO SAVE FOR THE TOP FINISH. BEFORE FILLING IN THE CONCRETE, STRIPS OF WOOD HAVING STRAIGHT EDGES ON TOP MUST BE NAILED TO THE STAKES ON BOTH SIDES OF THE WALK, AS I SHOWED YOU ON THE BLACKBOARD IN FIG. 1, MARKED A A. THESE STRIPS MUST BE PLACED AT PROPER GRADE IN THEIR LENGTH, AND LEVEL ACROSS FROM ONE TO THE OTHER. A STRAIGHT EDGE MADE OF WOOD, AND LONG ENOUGH TO REACH OVER THE WALK, AND THE STRIPS AS WELL, MUST BE PROVIDED, AND IT MAY BE NOTCHED OUT AS I SHOW AT X, IN Fig. 1. THIS STRAIGHT EDGE IS TO BE USED IN LEVELLING OFF THE TOP OR FINISHING COAT, BY KEEPING BOTH ENDS ON THE STRIPS A A, AND MOVING IT ALONG LENGTHWISE OF THE WALK. IF THE TOP OF THE WALK IS TO BE BELOW THE EDGES OF THE STRIPS, you may notch the ends, as shown, to suit whatever depth may be required." FRED TOLD HIS FATHER HE THOROUGHLY UNDERSTOOD THE PROCESS AS FAR AS EXPLAINED, AND THE LATTER THEN LEFT. BY THIS TIME NICK AND GEORGE—AND, WE MIGHT ADD, JESSIE—HAD WHEELED INTO THE TRENCH QUITE A LOT OF GRAVEL, BUT FOR THE WANT OF A PROPER "TAMPER" THEY HAD TO STOP. SO FRED CUT TWO PIECES OFF A FENCE POST, EACH ABOUT A FOOT LONG, AND WITH AN AUGER OR BORING TOOL, MADE A HOLE IN THE CENTRE OF THE END OF EACH, ABOUT EIGHT INCHES DEEP, INTO WHICH HE INSERTED A ROUND WOODEN HANDLE, ABOUT THREE FEET LONG. THESE MADE EXCELLENT "TAMPERS," NOT TOO HEAVY FOR GEORGE TO USE. JESSIE, PERSUADED FRED TO MAKE HER "JUST A LITTLE ONE," BUT HE TOLD HER NOT TO USE IT MUCH OR HER HANDS WOULD GET SORE AND TOO STIFF TO PRACTISE HER music. THE STRIPS FOR THE STAKES WERE PREPARED, NAILED ON, AND PROPERLY ADJUSTED, AND THEN IT WAS TIME TO COMMENCE THE REAL work. Nick had nailed some boards on three pieces of scantling about six feet long, which made a good mixing table for THE CONCRETE. THIS WAS CARRIED UP NEAR THE TOP END OF THE WALK, AND PLACED WHERE IT WOULD BE HANDY. A PAILFUL OF CEMENT WAS PUT ON THE BOARD, NEXT TWO PAILFULS OF NICE CLEAN SAND, AND THEN FIVE PAILS OF GRAVEL THAT HAD NO STONES IN IT LARGER THAN WOULD PASS THROUGH A RING HAVING A CLEAR DIAMETER OF TWO INCHES. ALL THIS GRAVEL, SAND, AND CEMENT BEING IN ONE HEAP ON THE BOARD, FRED AND NICK WORKED AT IT STEADILY FOR MORE THAN TEN MINUTES, MIXING IT UP UNTIL THE SAND AND CEMENT WERE THOROUGHLY AND EVENLY BLENDED WITH THE GRAVEL. FRED THEN SPRINKLED THE MIXTURE WITH CLEAN WATER FROM THE HOSE, WHILE NICK KEPT SHOVELLING IT OVER AND OVER UNTIL THE WHOLE WAS DAMP, BUT NOT SO MUCH SO THAT THE CEMENT AND SAND WERE WASHED FROM THE GRAVEL. THE WHOLE MASS LOOKED LIKE A PILE OF DIRTY STONES THAT HAD JUST BEEN UNDER A LIGHT shower. "THIS," SAID FRED TO NICK, "IS A VERY IMPORTANT PROCESS, FOR IF WE MAKE THE STUFF TOO WET, IT WILL STARVE THE CONCRETE BY washing away the cement, and if we leave it too dry the work will be rotten and crumble away." FRED MIGHT ALSO HAVE ADDED THAT THE PROPER PROPORTIONING OF THE MATERIALS WAS AS ESSENTIAL AS THE PROPER MIXING, AND IN THIS CASE, WHERE WE ARE MAKING IT ONE OF CEMENT, TWO OF SAND, AND FIVE OF GRAVEL—ALL BY MEASUREMENT—WE MUST adhere closely to the rule or the walk will be uneven in texture and colour. THE CONCRETE BEING PROPERLY MIXED, FRED AND NICK BEGAN TO SHOVEL IT INTO THE TRENCH, SPREAD IT TO ABOUT FOUR INCHES IN thickness, and tamped it down until the top mass looked sloppy and muddy. While in this condition, a new lot of cement MIXTURE WAS MADE, CONSISTING OF ONE PART OF CEMENT AND TWO PARTS OF SAND AND THE FINE OF THE GRAVEL THAT HAD BEEN SIFTED. ALL WERE MIXED THOROUGHLY WHILE DRY, AND AFTERWARD WET TO THE CONSISTENCY OF THICK MORTAR. THIS WAS SPREAD OVER THE CONCRETE TO ABOUT ONE INCH IN THICKNESS AND LEVELLED DOWN BY THE NOTCHED STRAIGHT EDGE UNTIL THE PROPER THICKNESS AND LEVEL WERE OBTAINED. THE SURFACE WAS THEN READY TO SMOOTH, OR "FLOAT," AS THE WORKMAN CALLS IT, WHICH ALWAYS GIVES TO THE TOP OF THE WORK A NICE, EVEN, LEVEL APPEARANCE, AND MAKES IT SOLID AND FIRM. THE "FLOATING" IS DONE WITH A TOOL MADE OF WOOD, AS SHOWN IN FIG. 7, AND MAY BE FINISHED OFF WITH A PLASTERER'S STEEL FLOAT, MERELY TO GIVE THE SURFACE A better finish. THE FLOATING OPERATION IS LABORIOUS, FOR IT MUST BE DONE AT ONCE, WHILE [29] [30] [31] [32] [33]