Page:Popular Science Monthly Volume 14.djvu/263

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its course, the leaf follows, but the reason is always a diminished tension on the illuminated side. This is true of the stalk as well as of the flower. Hence the two phenomena of periodic movement and of heliotropism depend on variations in the quantity of the glucose contained in the point of movement.


Value of the Robin to the Agriculturist.—Like the English sparrow, the "robin" (Turdus migratorius) has human enemies and detractors who will not admit that he is of any use whatever to the gardener and fruit-grower; but assert that he prefers to grow fat on stolen cherries and other small fruits, rather than on an insect-diet. But what are the facts? Lieut. D. A. Lyle, U. S. A., reared a robin from the fledgling state to maturity, in the mean time closely studying the bird's preferences in the matter of food, and here is the result of his observations, as communicated to the American Naturalist: On being taken from the nest, the young bird was placed in a cage, with plenty of boiled eggs and mashed potatoes and pure water. He would neither eat nor drink, but sat drawn up in the bottom of the cage, giving vent to an occasional chirp. The food was then forced down his throat, and this treatment revived the patient somewhat, but did not give entire satisfaction. He then received raw beefsteak three times a day, with bread and egg at intervals. The effect was striking: the eyes brightened, the chirp became loud and strong, and the bird would hop about briskly. He soon learned to open his mouth for the food. Next he was for three days restricted to a diet of earthworms, of which he would eat his fill, and then retire moodily to a corner, there to remain for about fifteen minutes, till the meal was digested. But, as this food acted as a purgative, it was alternated with beefsteak. The June beetle being then in season, that species of food was tried, and the bird preferred it to anything else. As long as June beetles could be procured, they constituted the sole food of the bird, and he thrived marvelously on it. Every day he consumed forty to fifty of these large beetles. "One morning," writes Lieut. Lyle, "at seven o'clock I gave him fifteen; I returned from the office at twelve, and from that time until sunset I fed him all he could eat. During this time he disposed of seventy-two of the large beetles!" When the June bugs were no longer to be had, cherries were given to the bird. These, when he was hungry, he would eat greedily, but they were speedily rejected when a few coleoptera or a piece of raw steak appeared in sight. The author then makes an estimate of the number of insects probably destroyed per diem by the twenty-three pairs of robins occupying the grounds around his residence, taking as the basis of his calculation the performance of his captive robin, and finds that the number would be at least 4,600, or 138,000 per month! Examination of the cherry-trees growing on the grounds showed that only about one cherry in twenty had been injured by the birds—a very low price to pay for their service in exterminating the noxious insects.


Gelatine as a Food-Preservative.—Dr. Campbell Morfit's "gelatine process" for preserving articles of food—as milk, vegetables, fruits, etc.—possesses many advantages which will undoubtedly win for it a very general acceptance. It consists in adding to the substances to be preserved a certain proportion of gelatine, and then drying the mixture till it does not contain over 10 or 12 per cent, of moisture. The mode of applying the process to the preservation of milk is described as follows in Nature: One pound of gelatine is dissolved in a gallon of milk at a temperature of 130° to 140° Fahr., and the solution is then allowed to set into a jelly, which is cut into slices and dried. By employing the product of this first operation in place of fresh gelatine for gelatinizing a second gallon of milk, a jelly is obtained in which the milk solids are just doubled in amount. As a gallon of milk contains about 6,400 grains of these solid matters, viz., casein, milk-sugar, milk-fat, and phosphates, their ratio to the gelatine will become as 12,800 to 7,000 after the second operation just described. If, then, the dried milk jujube, as it may be now called, be again and again employed with successive quantities of milk, a limit is reached when the one pound of gelatine has been incorporated with ten gallons. At this stage the mixture will contain no more than one part of gelatine