The Boy's Book of New Inventions

by Harry E. Maule

First, however, before building the mould for a residence, school, theatre, office building, or factory, the engineer decides what strength his foundations must have. The foundation for a small residence is an easy matter, but when it comes to a big factory, or an office building of a dozen stories or so, the most careful work must be done beforehand. In the old days, when it was desired to sink the foundations of a building down to bedrock, they used steel or wooden piles, but these will rust or rot, and the modern way is to use concrete piles. Either the great poles are moulded first and sunk like the ordinary wooden ones, or a pipe with a sharpened point is sunk and the concrete deposited in it by buckets designed for the purpose. Once these piles are driven, they are there for all time, if the work is done properly, and the engineer can be sure that his building is as good as if resting on bedrock.

From then on the erection of a reinforced concrete building is a most intricate matter, because while concrete in itself is a very simple substance, its use in buildings is a highly developed science. Of course there are many different methods of using concrete, and each one prescribes a different kind of steel network for the reinforcement. Then, too, some engineers cast parts of their buildings separately and put them in place after they have set, while others run the concrete for beams, floors, and walls into moulds, built right where those parts are to be in the finished structure. In laying the steel reinforcing rods, before the concrete is poured, the engineer sees that they make a perfect network so as to take care of all the strains, just as they will be put upon the building when it is completed. It is in the proper placing of reinforcement that the greatest engineering knowledge is needed in this kind of building.

As the wooden moulds for the first foundation beams and girders are completed and the reinforcement is placed, the concrete is poured in. The subcellar or cellar floor mould then is laid, the reinforcement placed and the concrete run in. Next the moulds for the cellar walls are built and perhaps the moulds for the beams and girders for the first floor. The reinforcing rods are placed in these moulds and the concrete run in, and so on, a story at a time, or a small section at a time, until the structure reaches the height called for in the plans, and it stands completed. As the building progresses and the concrete on the lower floor sets, the moulds can be taken down and used on higher stories. Concrete is even used for the roofs of buildings, as it can be moulded right in place or set up in slabs that can be later cemented together.

When properly used reinforced concrete is absolutely fireproof, so it is coming into extensive use in the construction of schools, theatres, warehouses, factories, and all other such buildings where a great height is not required. So far, none of the great skyscrapers has been built of reinforced concrete, although office buildings of sixteen stories have been erected with complete success.

There is still another method of using concrete as a building material. This is in the form of building blocks, and doubtless all who read this will recall seeing many beautiful residences built of blocks of stone that on closer inspection proved to be concrete. The blocks can be cast in any size or form and used in just the same way as structural stone.

Now, after having looked about the city and having seen the numerous ways that concrete is used as a building material, we come back to the very latest thing in the use of this man-made stone—the "one-piece" or poured house.

For a good view of it let us take a little jaunt out to West Orange, N. J., with the scientist and look into the library of Thomas A. Edison's laboratory, where we will see a perfect model of this marvel of invention. It is practically the same as the one at the cement show. Standing in the centre of the great room where Edison works is this perfect little cottage, about the size of a large doll's house. It represents not only Edison's latest invention, but also his favourite scheme. In years to come, when the boys who read this are grown men, it will probably be no novelty to build houses by pouring them all at once into a steel mould, but just at present it is one of the most startling developments in an age of epoch-making inventions.

Every boy knows that Edison has never followed the ideas of others in working out his inventions, and the poured house is no exception to his rule. It will be interesting to take a little look back over a part of Edison's life and see how he came to enter the cement-making business, and how, when he had his process down to a fine point, he said to himself, "It is cheap and easy to build a house or an office building of concrete in sections, why not build it all in one piece?"

We shall see that no sooner had he asked himself this startling question than he began by making models, and satisfied himself that it was not only possible, but one of the cheapest and best methods of making small, simply arranged houses, such as could be bought or rented for a small sum.

Although Edison has within the last few years brought his idea to a state where it can be put to practical use, he himself is not trying to push it commercially, as he has his other great inventions like the phonograph, storage battery, and the motion-picture machine. In fact, he is content to let it be worked out by others just so long as it fulfills his idea of giving to workingmen good houses at a low price.