Page:Popular Science Monthly Volume 20.djvu/152

142 springs, must be avoided. The worst enemy of sponge-culture is mud. The sponges chosen for cutting must be gathered by experienced hands, with all possible gentleness, so as to avoid tearing them. They should be cut up rapidly, with a common knife, or, better, a saw-like blade, being laid for the purpose on a smooth wooden board, moistened with sea-water, into pieces of about one cubic inch each; and it is well that each cutting should have the greatest possible area of uninjured outer skin. A healthy piece of sponge firmly attaches itself to any surface with which it comes into intimate contact, in a short time. Preference is given to stone as a foundation, because it is the natural ground and is not attacked by the teredo, which seems to be a dangerous enemy to the culture. The Austrian culturists generally attached their cuttings by pegs to a kind of wooden apparatus, taking care to avoid lacerating the sponge, and forcing and squeezing, which cause a loss of sarcode, and metals, which cause rot, and sink it into the water. Too much light and too little light must be avoided; the sponges must be kept constantly moist with seawater during the preparation, especially in warm weather; and all wood-work must be tarred, to delay (for it does not prevent) the ravages of the pile-worm. If the cuttings hold fast after three or four weeks, the propagation is regarded as secure. A characteristic feature is the tendency of the cuttings to assume a round form, and the apparatus for planting them is shaped to promote this. The period of growth varies considerably, but generally a term of seven years is required to produce a marketable and profitable article. The question whether this mode of cultivation is profitable appears to have two sides. Dr. Marenzeller considers it doubtful whether it is advantageous to cut in pieces a sponge which, uncut, would have more quickly reached the same size and height as the collective cuttings, and thinks that attention may be better directed to the development of ill-shaped ones into good-shaped ones.

Experiments in Vision.—MM.Macé and Nicati have found that persons with normal vision, when looking at the solar spectrum, form considerably different estimates of the distribution of light in it. They have since experimented with four Daltonians, or color-blind persons, and observed that in three of them the vision of red was very feeble, that of yellow was normal, and that of green appeared to be even sharper than in normal-eyed persons, while in the fourth the conditions were reversed. Between Daltonians who could not perceive red, differences were noticed in the powers of vision of blue and violet, similar to those met in normal eyes. M. Charpentier has experimented by looking in darkness at an opaque screen perforated by a number of minute holes, which were distinguishable in a moderate light, and learned that a very faint light merely produces a diffuse luminous sensation; a greater quantity of light gives the notion of color, if color is present; and a still greater quantity is required to produce the perception of form.

The Interstellar Ether.—Professor T. Sterry Hunt, at the recent meeting of the American Association, explained his peculiar views of the nature of the interstellar ether. Having referred to the theories of different philosophers respecting the extent of the earth's atmosphere and the nature of the ethereal fluid, he said that processes have been going on from the earliest ages which have absorbed and evolved enormous quantities of gases. For instance, in the manufacture of the limestone rocks of the earth alone over two hundred times the amount of the carbonic dioxide now in our atmosphere have been consumed. This must have been borrowed from space. Professor Hunt then discussed the probability of a chemically compound ether, exceedingly attenuated, existing in the interstellar space, and pervading the universe just as the atmosphere surrounds the earth.

Vaccination for the Anthrax.—After a long series of experiments M. Pasteur has found a method of attenuating the virus of the carbuncle, or anthrax, of cattle and sheep, and of vaccinating animals with it so as to give them an effective protection against the disease. The sufficiency of the remedy was attested by inoculating with the active virus sixteen sheep, taken as they came from the flock, and nineteen