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THE POPULAR SCIENCE MONTHLY. 



terranean 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 gen- 

 tleness, 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 it- 

 self to any surface with which it comes into 

 intimate contact, in a short time. Prefer- 

 ence is given to stone as a foundation, be- 

 cause it is the natural ground and is not 

 attacked by the teredo, which seems to be a 

 dangerous enemy to the culture. The Aus- 

 trian culturists generally attached their cut- 

 tings 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 sea- 

 water 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 char- 

 acteristic feature is the tendency of the cut- 

 tings to assume a round form, and the ap- 

 paratus for planting them is shaped to pro- 

 mote 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 

 ti > 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. Alace 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 Dal- 

 tonians who could not perceive red, differ- 

 ences were noticed in the powers of vi- 

 sion of blue and violet, similar to those met 

 in normal eyes. M. Charpentier has experi- 

 mented by looking in darkness at an opaque 

 screen perforated by a number of minute 

 holes, which were distinguishable in a mod- 

 erate 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 pro- 

 duce the perception of form. 



The Interstellar Ether. Professor T. 

 Sterry Hunt, at the recent meeting of the 

 American Association, explained his pecul- 

 iar 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. Pro- 

 fessor Hunt then discussed the probability 

 of a chemically compound ether, exceed- 

 ingly attenuated, existing in the interstellar 

 space, and pervading the universe just as 

 the atmosphere surrounds the earth. 



Vaccination for the Anthrax. After a 



long scries 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 



