In some buildings, such as an old country church which I attended for many years, the architect had openly acknowledged the tendency of the walls to fall outward, and had counteracted it by a series of great beams extending completely across the nave and aisle. As he had not even troubled himself to hide their office, so he did not trouble himself to conceal the fact that they were tree-trunks, but left them roughly squared with the axe, lest, if he had squared them throughout their length, he should have diminished their strength.
The effect of the partially squared beam is, of course, far more picturesque than that of a completely squared one. The architect, however, need not have been so careful about strength, for if the beams had been only half their diameter they would have been just as effective. The strain on them is by pulling, and not by pushing. Now, as any one can see by trying the experiment with a splinter of wood—say a lucifer-match—an enormous power is required to break it by tearing the ends asunder, while it can be easily broken by pushing them towards each other.
But for this power of resistance, we should never have had our Crystal Palace. That apparently intricate, but really simple (and the more beautiful for its simplicity), intersection of beams and lines diminishing in the distance to the thickness of spiders’ webs, is nothing more than a combination of the Girder and Tie, the two together combining lightness and strength in a marvellous manner.
The story of the Crystal Palace is now so well known that it need not be repeated in detail. A vast building was required for the Exhibition of 1851, and not an architect was able to supply a plan which did not exhibit some defect which would make the building almost useless.
Suddenly a Mr. Paxton, who was a gardener, and not an architect, produced (on a sheet of blotting-paper) a rough plan of a building on a totally new principle, and not only fulfilling all the requisite conditions, but being capable of extension in any direction and to any amount. There have been very few bolder conceptions than that of making iron and glass take the place of brick, stone, and timber, and the result fully justified the expectations even of the inventor.
How a gardener suddenly developed into an architect remains to be seen; and, indeed, in this case the architecture was the result of the gardening, or rather, of practical botany applied to art. Some years before the invention of the Crystal Palace, that magnificent plant, the Victoria Regia, had been introduced into England. Its enormous leaves, with their wonderful power of flotation, caused a great stir at the time, and some of my readers may remember a sketch which was engraved in the Illustrated London News, and which represented a little girl standing on one of these leaves as it floated on the water.
Mr. Paxton saw how this power was obtained, and the result was that he copied in iron the lines of the vegetable cellular structure which gave such strength to the Victoria Regia leaf, and became more eminent as an architect than he had been as a gardener. The capabilities of the Crystal Palace had lain latent for centuries, but the generalising eye of genius was needed to detect it. A thousand men might have seen the Victoria Regia leaf, and not thought very much of it; but the right man came at the right time, the most wonderful building in the world sprang up like the creation of a fairy dream, and the obscure gardener became Sir Joseph Paxton.
I have no doubt that thousands of similar revelations are at present hidden in Nature, awaiting the eye of their revealer.
Now we come to the principle of the Buttress, i.e. giving support to the exterior, instead of the interior, and strengthening the walls by pushing them together, instead of pulling them together.