It is, perhaps, needless to give more than a passing reference to the Suspension-bridges made by Spiders, by means of which they can traverse considerable distances. The similar bridge of the Little Ermine Caterpillar has already been mentioned, when treating of the subject of Double Walls.
ARCHITECTURE.
CHAPTER IV.
LIGHTHOUSES.—THE DOVETAIL.—THE DAM.—SUBTERRANEAN DWELLINGS.—THE PYRAMID.—MORTAR, PAINT, AND VARNISH.
The Eddystone Lighthouse: its Position, and the Difficulties of building it.—Destruction of successive Lighthouses.—Smeaton’s Idea of Form borrowed from the Tree-trunk.—Mode of building.—Rooting it into the Rock.—Principle of the Dovetail.—Bones of the Human Skull, and their Articulation.—The Dam, and its Uses to Man.—The Lock and the Water-mill.—Dam of the Beaver: its Objects and Mode of Construction.—Popular Errors with regard to the Dam.—Subterranean Dwellings.—The Indian Palace, and its Use in Summer.—Subterranean Dwellings in Kamschatka, and their Use in Winter.—The Wood or Horse Ant, and its double Dwelling.—The upper and lower Nests used according to the Amount of Warmth required.—Section of the Nest, and a Glimpse into its Interior.—The Pyramid.—Derivation of its Name.—Natural Objects from which the Form was derived.—Subaquatic Mortar or Cement, and its Use to Man.—Subaquatic Cement used by the Caddis, the Stickleback, the Terebella, the Sabella, the Serpula, and others.—Paint and Varnish, and their Utility to Man.—Propolis as used by the Hive Bee, and the Source whence it is obtained.
WE now come to some points in Architecture which cannot well be grouped together, and must therefore be treated as Miscellanea.
Our first example is one which was avowedly based upon an imitation of Nature, namely, the celebrated Eddystone Lighthouse, and we shall see that in two points—first its form, and next the mode in which the stones were fixed together—Nature had been closely followed by the architect.
Unlike ordinary lighthouses, this edifice had to be constructed so as to endure the full force of waves as well as wind. A few miles from the southern coasts of Devon and Cornwall there is a rock which in former times greatly endangered the ships which passed along the Channel. Several attempts were made to build a lighthouse on this dangerous spot. Winstanley’s lighthouse, which was finished in 1700, was wholly swept away three years later, together with the architect himself, and some workmen who were engaged in repairs. So terrific is the force of the elements on this spot, that the lighthouse was entirely destroyed, and the only vestiges of it that were ever discovered were some iron bars and a piece of chain.
Another lighthouse was built a few years afterwards, but was burned down, it being of wood instead of stone. At last the work was put into the hands of Smeaton, who saw that he must build on a totally new plan. He took for his model the trunk of a tree, and determined to build his lighthouse of the same form as the tree-trunk, and to fasten it into the rock just as a tree is fastened by its roots. Accordingly, he struck out a new principle in the construction of such edifices, and his model has been followed ever since. The reader will see, by a glance at the illustration, how close is the resemblance in external form. I may mention that the tree in question was sketched from one in a paddock opposite my house.
Having settled the form of the lighthouse, and made it like a tree-trunk, the next business was to fix it firmly in the rock, and, in fact, to give it roots of stone. For this purpose, he made the base of the edifice as wide as the rock would allow, so as to correspond with the wide base of a tree-trunk, and traced a circle of about ninety feet in circumference. Instead, however, of merely laying the stones as is usually done, or even letting them into holes cut in the rock, he hit upon a singularly ingenious device, whereby the building was practically a single stone.