Why Wool felts.—The cause of the felting properties of wool is generally attributed to serratures on the surface of the fibers, which are supposed, when driven into the closest possible contact, to hook into one another, and so to hold together by what might be called a "beggar's-lice grapple." The validity of this theory was called into question by two gentlemen of Hartford Captain George R. Case, a microscopist, and Mr. Joseph Dawson, a woolen manufacturer. These gentlemen, obtaining samples of wool of different grades, subjected them to various manipulations, and found: 1. That a single fiber of wool, when manipulated by itself in a lubricant of soap, has no fulling property, but rather a tendency to lengthen the fiber; 2. That a number of fibers placed side by side, just as they grew on the sheep, and with simply tension enough to take out the kinks, when manipulated with a lubricant of soap, have no felting property, 3. That fibers similarly treated, but with the roots and tips alternating, have no fulling or felting property, and no power of adhesion; but, 4. That a number of fibers placed side by side, with the tips all one way or with the roots and tips alternating, without any tension, have fulling properties; and, 5. That fine-carded wool, taken from a second breaker, with the fibers thoroughly mixed, has great fulling properties when properly manipulated. A sample of negro's hair of suitable length, which was found by microscopical examination comparatively free from serratures but slightly spiral in structure, manipulated in the same manner as the wool had been, was formed into a "well-felted sample of cloth." These and other experiments satisfied the authors that the fulling properties of wool or any other fibers were in proportion to the number of waves, curls, or kinks, and their degree of fineness, and that the serratures, per se, have little to do with the matter, excepting possibly that which may be due to friction. "To the question, What is the cause of the fulling or felting of wool? the simplest answer possible is, it is the looping and interlooping, locking and interlocking of the fibers until they become inextricably entangled, but by interlooping and interlocking, and not upon the beggar's-lice principle."
Spade-Foot Toads.—Dr. Charles C. Abbott contributes to the "American Naturalist" a study of the hermit spade-foot toad (Scaphiophis Holbrooki), a rare animal, whose custom it seems to be to appear unexpectedly in numbers, and, after a few days, suddenly to disappear. Its name is derived from its long, horny index-toe, which may well be characterized as a spade, for it digs with it rapidly into the ground; and its voice, immense for so small an animal, is like a steam-whistle. The spade-foots first visited Dr. Abbott's field of observation in May, 1874, stayed a few days, and were gone. Their next visit, ten years having passed without a single specimen being seen or heard, was April 10, 1884, in the same spot, a sink-hole in a dry upland field near Trenton, N. J. They remained till the 15th, when the weather became cooler and they vanished. Again they came, June 26th, after a rain-storm that flooded the sink-hole, and were found sitting on the grass-tufts and swimming in the pond by the hundred, all uttering their shrill, ear-piercing groans, through the day and night; but on the morning of the 28th all were gone. During this brief visit the frogs spawned, and the eggs were found attached to blades of grass and slender twigs. In about a week, those of them which were not destroyed by the retiring of the water were hatched out into tadpoles very much like other tadpoles. As they grew, about five per cent of the number failed to develop as rapidly as the others. These "retarded" tadpoles were voracious cannibals, preying upon their fellows, now become "hoppers" and miniatures of the adult spade-foots, so extensively that it was necessary to protect them to save any. In due time, the water was removed from the aquarium, and earth put in its place to about an inch in depth. "Upon this the young spade-foots were placed, and in less than one minute many had commenced digging little burrows, into which they disappeared as the excavations deepened. . . . In twenty minutes all but two of forty-four specimens were below the surface." A few individuals remained in the sink-holes as the water dried up into puddles; but Dr. Abbott having neglected them, under the supposition that they would burrow where they were, for ten days, could find
