Page:Popular Science Monthly Volume 8.djvu/262

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250
THE POPULAR SCIENCE MONTHLY.

or spring species, fall ploughing under the trees, which breaks up their fragile cocoons that lie secreted in the soil, and in early spring scraping the trunks of the trees where their eggs are lodged in the crevices of the bark, are recommended. These measures fail with the fall sort, and, in the abstract of the paper now before us, nothing is suggested to take their place.

At the same meeting Prof Riley also presented a paper giving an account of some recent experiments with the grape phylloxera, undertaken for the purpose of determining when the winged female deposits her eggs. He built a tight gauze house six feet high and four square over a Clinton vine. The house was built so as not to permit even so small an insect as the winged phylloxera to get in or out, and the vine was trimmed so that but few branches and leaves remained to be examined. Into this inclosure he brought an abundance of infested roots, and from these obtained a supply of the winged females, confined where he could watch their ways. The result of these observations is that, as has been surmised, the eggs are often laid in crevices on the surface of the ground, but still more often on the leaves, attached generally by one end amid the natural pubescence of the under surface; and, while heretofore all efforts to artificially hatch the progeny from these eggs have failed, Prof Riley has this year succeeded in hatching them, and presented a tube filled with living females.

 

Condensed Beer.—A process for condensing beer, recently patented in England, is described as follows in the English Mechanic: Beer or stout is taken at any stage of fermentation, though the process is better applied when it is fit for drinking, and evaporated in a vacuum-pan until it becomes a thick, viscous fluid. The alcohol and water of course pass off in vapor, which, in turn, is condensed in a receiver, and the alcohol recovered by redistilling the liquid. This alcohol may be mixed again with the condensed beer. By this process of condensation, the beer is reduced to one-eighth or one-twelfth of its original bulk, and, as the fermentation is suspended by the heat employed, the condensed mixture will keep in any climate for any length of time. The process of reconverting the mixture into beer is also a simple one, consisting merely in adding the bulk of water originally abstracted, and setting up fermentation again by the use of a small quantity of yeast or other ferment. Within forty-eight hours the beer may be drawn from the tap for use, or bottled in the ordinary way; or, without using any ferment, the beer may be bottled, and charged with carbonic-acid gas

 

Is Consumption contagious?—Some experiments and observations recently made, on the transmission of tuberculosis or phthisis from one animal to another, are worthy of note, as indicating one fruitful source of pulmonary disease. Thus it has been found that when an animal with tuberculated lungs is made the yoke-fellow of a perfectly healthy animal, and the two are housed and fed together, so as to inhale one another's breath, the one which at first was sound, before long exhibits the symptoms of tuberculosis. Again, Krebs has produced tuberculous by giving animals milk from those which were diseased. In addition to rabbits and Guinea-pigs (which animals are very susceptible to the artificial production of the malady), he accidentally induced the disease in a dog by feeding it with the milk of a cow in the last stage of phthisis. As a result of his observations, he asserts that tubercle virus is present in the milk of phthisical cows, whether they are slightly or gravely affected. On vigorous subjects such milk may produce no injurious effects, but the case is likely to be different with children, and those of enfeebled constitution. Similar effects may result from eating the flesh of animals affected with tubercle, and by inoculation with the virus. Thorough cooking of milk and flesh-meat neutralizes their injurious action.

 

Continuity of the Guano-Deposits.—Are guano-deposits of recent formation, or do they date from a geological epoch prior to the present? The latter opinion has been held by many eminent scientific men, among them Humboldt. The observations of Boussingault, however, go to prove the recent origin of these deposits. One fact, cited by Boussingault in support of this theory, is the existence in the guano of the bodies of birds