Page:Popular Science Monthly Volume 13.djvu/393

Rh side, seems, as it issues from the doors and windows of the stone houses, to pause in mid-air like a droning bee. Then scores of busy figures repair with their water-vessels to the verge of the steep bluffs, and disappear in the crevices of the rocks below."

How Monkeys dislike Snakes.—That monkeys, like man, have a peculiar instinctive abhorrence of snakes, is shown by an experiment made in the Philadelphia Zoological Garden by Mr. Arthur E. Brown, and recorded in the American Naturalist. Mr. Brown having wrapped a dead snake in paper, set the package on the floor of a cage containing forty or fifty monkeys. It was instantly spied by a female cynocephalus, who quickly seized the paper and dragged it away with her. Soon the paper unfolded and the snake slipped partly out. On seeing what the package contained, the cynocephalus instantly dropped it and sheered off. The other monkeys now cautiously approached the dead snake, but all were careful not to come too near, with the exception of one, a large macaque, who would make an occasional snatch at the paper, as though to see whether the dreaded animal were really dead. A pull on a string attached to the tail of the snake, causing it to stir, sent the inquisitive monkeys scampering away, but they would again return, ever keeping at a respectful distance. The dead snake was then successively introduced into cages occupied by animals of other orders—carnivores, rodents, ungulates, etc.—but none of them paid it any special attention except one peccary, which, finding that it was dead, seemed disposed to eat it. The author observed in a deaf and dumb lady the expression of the same emotions and feelings, on beholding serpents, which had been exhibited by the monkeys. There were the same fear, the same attraction and repulsion; and after watching for a long time, with an expression of intense disgust, a cage of boas, she was led away by her friends, protesting that she wanted to stay.

Discoloration of Brick Walls.—Brick buildings, in the neighborhood of New York, are often seen disfigured by streaks and patches of white; but it is in Philadelphia that the evil is most noticeable. There these white incrustations are very general on brick house-fronts, and the study of their causes and their remedy has for some time engaged the attention of builders. Mr. William Trautwine is, so far as we know, the first who has attempted a thorough, scientific investigation of the subject; and his observations, published in the Journal of the Franklin Institute, are eminently worthy of the attention of architects in localities where this disfiguration makes its appearance. The evil, he says, is most noticeable in dry weather on parts of walls subjected to dampness, and on entire walls after rain-storms have soaked them. The white coating is derived primarily from both the bricks and the mortar. In some instances it undoubtedly comes from the bricks; here the white substance is dissolved by moisture from the bricks even before they are built into the houses. The author has found it in bricks just from the kiln. It has a peculiar taste—that of sulphate of magnesia; but besides this salt the bricks also contain sulphate of lime. The author's theory is that the silicates of magnesia and lime in the bricks are converted into the sulphates by the sulphuric acid evolved from the sulphide of iron and iron pyrites contained in the coal which is employed in the kilns. Now, sulphate of magnesia effloresces in dry air, and sulphate of lime is dissolved by moisture and appears on the surface of the bricks. Hence, plainly, one mode of preventing the incrustation is the employment only of wood or of coke free from sulphur in the kilns—at least this might be done in the manufacture of pressed brick for house-fronts. As for the incrustations having their origin in the mortar, the author remarks that sulphate of magnesia is largely produced by the decomposition of mortar. His observations on this head have special application to Philadelphia and its vicinity, where most of the lime used in building is from magnesian limestone. The resulting mixture of limestone and magnesia, when slaked and made into mortar, is very susceptible to the influence of sulphurous fumes in the atmosphere, which produce in the mortar sulphates of lime and magnesia. The great solubility of sulphate of magnesia facilitates its diffusion; sulphate of lime is comparatively insoluble, and does not cause so much disfigurement. Of course, mortar made with lime from magnesian limestone quickly decomposes,