Page:Popular Science Monthly Volume 6.djvu/391

 the use of a stiff brush, with sand. Having thus taken out of the pond, cleaned, and returned again to the water, many hundred fish, it was discovered that the labor was in vain, for the parasites were so numerous that soon the fishes were infested again. The crustaceans plainly were holding their own. Mr. Buckland now cleared away the mud in front of the pipe, so that the fish might have a chance of rubbing off their tormentors against the bottom. He next conceived the idea of spreading a quantity of gravel about the pipe. With the aid of this and an abundant supply of fresh water at a low temperature, the fish were enabled to rid themselves of their parasites easily, and, in the cooler water, the latter did not find the conditions of life so favorable.

A Worm that the Sparrows refuse.—We recently noted the appearance in the public parks and squares of Philadelphia of a caterpillar which threatened to destroy the thethe [sic] trees. The English sparrow had effectually exterminated the measuring worm in those parks, but showed no disposition to attack this new destroyer of the foliage. At the late meeting of the American Association, Dr. John L. Le Conte described this insect as the larva of the moth Orgyia leucostigma. It is a slender caterpillar, covered with stiff yellow-and-black hairs. The sparrow does not attack it, being deterred, probably, by the bristles, by which it is protected. But, fortunately, the nuisance can be abated without the aid of the sparrows. When the caterpillar has attained its full growth on the tree, it crawls to a neighboring wall or fence, and there, fixing its cocoon, undergoes transformation. The remedy against the annoyance is now very simple, viz., by sweeping the cocoons from the walls and fences with stiff brushes, and placing around the trees rings of tin-plate inclined at an angle. This will give the trees immunity, because the insects are not provided with wings for flight.

A New Source of Illuminating Gas.—An oil-bearing shale of considerable thickness, called Kimmeridge coal, or clay, underlies the whole county of Dorset, and is met with in other parts of England. Various attempts have been made to utilize this deposit for the purpose of producing light and heat, but with little success hitherto. Now, however, the Rev. Henry Moule has succeeded in devising a method of producing from it a good, useful gas. The new gas is obtained by the destructive distillation of the shale, the gaseous products being submitted to purification before use. In this latter process, as also at other stages of the manufacture, chalk is used. The gas itself, though not odorless, is by no means so pungent nor so unpleasant as ordinary coal-gas. During combustion no odor is perceptible, and, so far as can at present be ascertained, the products of combustion contain no noxious gases. Besides the gas, a pungent oil is produced, which Mr. Moule believes can be rendered comparatively odorless, and may with advantage be applied to various purposes. The inventor also proposes to utilize the heat-giving properties of shale and chalk for heating, both by means of gas and in a direct manner, his plans having been matured in this respect.

Contagious Ophthalmia.—In English poor-houses and "pauper-schools," contagious ophthalmia has, from the foundation of such institutions, afflicted the inmates. It is produced by unsanitary conditions of life—want of cleanliness, overcrowding, ill-ventilation, etc. It might be supposed that these establishments would have been greatly improved in later times, owing to the increased attention now bestowed on public hygiene; but the contrary is the fact, as we learn from a discourse by Dr. Brudenell Carter. A serious charge is brought by this gentleman against the Poor-Law Board, viz., that during the last few years their unwisdom has developed this malady in workhouses and pauper schools "in a manner to which previous English experience affords no parallel." The Government has refused to let the truth be seen, but Dr. Carter has been able to obtain, from a private source, a copy of a report made to an official inspector by the medical officer of one of the schools. It states, among other curious matters, that, of 1,062 children in the school in