Page:Popular Science Monthly Volume 2.djvu/783

Rh that temperature is not the only condition modifying vegetal growth at varying altitudes, but that varying degrees of atmospheric pressure have also a controlling influence in this respect. Some grains of wheat were sown in bell-glasses with all the conditions identical, save that the contents of one glass were subjected to the normal pressure of the atmosphere, those of another to two-thirds the ordinary atmospheric pressure, and those of a third to one third the ordinary atmospheric pressure. The first grains sent forth shoots 20 centimetres (7 inches) long, the second 5 inches, and the third did not come up at all. Again, with a pressure of 5 atmospheres, the plants did not come up, the radicles only having been sent out, and on opening the vase a strong alcoholic odor was perceived, in place of the ordinary acetic odor of putrefying wheat. After a few days a mould made its appearance.

Electric Detonators for exploding Mines.—Two new electric detonators, for exploding mines, one for land and the other for marine service, have been introduced in England. The former consists of a tin tube filled with fulminating mercury, and having a head of beech-wood. The electric wires run through this head, being insulated by gutta-percha, and their extremities held apart. In the space between the ends of the wires, and in contact with the fulminating mercury, is loosely packed a little gun-cotton, which is ignited by an electric current. The marine detonator has also a tube of tin filled with fulminating mercury, as also a beech-wood head. From tip to tip of the wires extends a platinum wire $3/10$inch long, and 0.003 inch thick, in a bed of loose gun-cotton. The electric current heats the platinum, thus igniting the gun-cotton and exploding the fulminant, which in turn explodes the powder.

Development of Vibrio-Life.—In the course of his very interesting experiments on protoplasmic life, Dr. Grace Calvert shows that a solution of albumen from a new-laid egg, in pure distilled water, does not develop protoplasmic life, when the atmosphere is shut out. If, however, it be exposed to the atmosphere for from 15 to 45 minutes, minute globular bodies will appear, which have an independent motion. The time required for these bodies to develop is proportioned to the surface exposed, as was shown by Dr. Calvert, who experimented with two portions of albumen, 400 grains each, one in a test-tube of three-fourths inch diameter, and the other in a test-glass showing a surface of liquid two inches in diameter to the atmosphere. In the tube, vibrios appeared after twelve days, but in the glass after five. With undistilled water, they appeared in the test-tube within 24 hours. Further, M. Pasteur having shown oxygen to be necessary to the life of the mucedines, Dr. Calvert shows that it is no less necessary to the existence of vibrios. To confirm this, he put into each of five glass bulbs a solution of albumen in water, the first being left in contact with the atmosphere 24 hours, and the ends of the tube then hermetically sealed about two inches on each side of the bulb. The other tubes were similarly closed, after passing oxygen, hydrogen, nitrogen, and carbonic acid, over the solutions. The tubes remained closed for 27 days, during which period the albumen in contact with oxygen was seen speedily to become turbid, and then that in contact with air, while the other three remained clear. The tubes were then broken, and it was found that those containing oxygen and common air held a large amount of vibrio-life, while those containing nitrogen, carbonic acid, and hydrogen, held but very small quantities; hydrogen least of all. Thus it was proved that oxygen is an essential element to the production of putrefactive vibrios. The transition from globular protoplasms, or monads, as he calls them, into vibrios, and their ultimate transformation into microzyma, is then described by Dr. Calvert. "A few hours after impregnation," says he, "the monads appear in the albumen, having a diameter of about $1/128000$ of an inch, and appear to form masses. Next, some of the monads are lengthened into vibrios, which have an independent motion, though still attached to the mass. As this motion prevails in this or in that direction, the mass is moved over the microscope-field. At last it is broken up, and soon each individual vibrio is seen rolling or swimming