Page:Popular Science Monthly Volume 7.djvu/581

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563
FRESH-WATER MOLLUSKS.

destructibility are desiderata, that it would be idle to attempt to categorize them.

The invention is being taken up practically on the Continent, and no less in England. Messrs. Powell, of Whitefriars, are introducing it in their glass-works, and two other firms in the north of England are doing the same. It is by no means improbable that its first introduction in practice in this country will be at the aquarium now in course of erection at Westminster, where it is intended to use it for the tanks.

There still remain some questions to be answered with regard to the phenomena exhibited by toughened glass—questions, however, which in no way affect the practical value of the material. Its peculiarities continue to form the subject of investigation, and, as soon as any conclusions of value to science have been arrived at, they will be made known, so that the physical aspect of toughened glass may again be reverted to in these pages. It only remains to observe that the re- markable character and unique nature of M. de la Bastie's invention are such as to render it probable that lie will not only materially benefit those of his own time, but will bequeath to posterity an invaluable legacy.—Popular Science Review.

 
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FRESH-WATER MOLLUSKS.[1]
By Prof. EDWARD S. MORSE.

UNDER lily-pads and on the stems and leaves of other aquatic vJ plants, and on stones in rivers, snails of various kinds will be found. A dipper with the bottom perforated, or made into a sieve, and attached to a wooden handle four or five feet in length, will be

PSM V07 D581 Snail collecting dipper.jpg
Fig. 1.—Dipper attached to a Wooden Handle for collecting Snails.

found useful in scooping up the sand or mud from the bottom of rivers and ditches. The dirt having been sifted out, the shells and other

  1. From "First Book of Zoology," now in press of D. Appleton & Co.