fossil tubes of Auvergne; an incrusting spring,
therefore, may, perhaps, be all that is wanting to reproduce, on the banks
of the Isis or the Charwell, a rock similar in structure to that of the
Limagne. Mr. Kirby, in his "Entomology," informs us, that these larvae
ultimately change into a four-winged insect. If you are desirous to examine
them in their aquatic state, "you have only, (he says) to place yourself by
the side of a clear and shallow pool of water, and you cannot fail to
observe at the bottom little oblong moving masses, resembling pieces of
straw, wood, or even stone--of the larvae itself, nothing is to be seen
but the head and six legs, by means of which it moves itself in the water,
and drags after it the case in which the rest of the body is enclosed, and
into which, on any alarm, it instantly retires. The construction of these
habitations is very various. Some select four or five pieces of the leaves
of grass, which they glue together into a shapely polygonal case; others
employ portions of the stems of rushes, placed side by side, so as to form
an elegant fluted cylinder; some arrange round them pieces of leaves like
a spirally-rolled riband; other species construct houses which may be
called alive, forming them of the shells of various aquatic snails of
different kinds and sizes, even while inhabited, all of which are
immovably fixed to them, and dragged about at pleasure. However various
may be the form of the case externally, within it is usually cylindrical
and lined with silk."--_Introduction to Entomology, by Kirby and Spence._

_Engraving on Glass._

Cover one side of a flat piece of glass, after having made it perfectly
clean, with bees' wax, and trace figures upon it with a needle, taking
care that every stroke cuts completely through the wax. Next, make a
border of wax all round the glass, to prevent any liquor, when poured on,
from running off. Then take some finely powdered fluate of lime (fluor
spar,) strew it even over the glass plate upon the waxed side, and then
gently pour upon it, so as not to displace the powder, as much concentrated
sulphuric acid diluted with thrice its weight of water, as is sufficient
to cover the powdered fluor spar. Let every thing remain in this state for
three hours; then remove the mixture, and clean the glass, by washing it
with oil of turpentine; the figures which were traced through the wax will
be found engraven on the glass, while the parts which the w