A recent number of Gill's "Technical Repository," contains a simple mode of consuming the smoke that ascends from the turner of an argand lamp. It consists of a thin concave of copper, fixed by three wires, at about an inch above the chimney-glass of the lamp, yet capable of being taken off at pleasure. The gaseous carbonaceous matter which occasionally escapes from the top of lamps, is thus arrested beneath the concave cap, and subsequently consumed by the heat of the flame, instead of passing off into the room, in the form of smoke or smut on the ceiling and walls.
[The "Technical Repository," may have the credit of introducing this contrivance to the British public; but it is somewhat curious that it had not been previously adopted, since scores of lamps thus provided, are to be seen in the cafés and restaurateurs of Paris. Apropos, the French oil burns equal in brightness to our best gas, and as we are informed, this purity is obtained by filtration through charcoal.—ED.]
Caddis Worms.
The transformation of the deserted cases of numberless minute insects into a constituent part of a solid rock, first formed at the bottom of a lake, then constituting the sides of deep valleys, and the tabular summits of lofty hills, is a phenomenon as striking as the vast reefs of coral constructed by the labours of minute polyps. We remember to have seen such caddis-worms, as they are called by fishermen, very abundant in the wooden troughs constructed by the late Dr. Sibthorp, for aquatic plants, in the botanic garden at Oxford, to the cases of which many small shells of the G. Planorbis Limnea and Cyclas were affixed, precisely in the same manner as in the 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 wax covered will be uncorroded. The fluate of lime is decomposed by the sulphuric acid, and sulphate of lime is formed. The fluoric acid, disengaged in the gaseous state, combines with the water that diluted the sulphuric acid, and forms liquid fluoric acid, by which the glass is corroded.
Habits of Seals.
The brain of this animal, observes Dr. Harwood, is I think, doubtless, of greater proportionate magnitude than in any other quadruped, and not only does it exhibit in its countenance, the appearance of sagacity, but its intelligence is in reality far greater than in most land quadrupeds: hence its domestication is rendered much easier than that of other animals, and it is susceptible of more powerful attachment. The large seal, which was exhibited some time ago at Exeter 'Change, appeared to me to understand the language of its keeper as perfectly as the most faithful dog. When he entered at one end of its long apartment, it raised its body from the water, in which it was injudiciously too constantly kept, supporting itself erect against the bar of its enclosure, and wherever he moved, keeping its large, dark eyes steadfastly fixed upon him. When desired to make obeisance to visitors, it quickly threw itself on one side, and struck the opposite one several times in quick succession with its fore-foot, producing a loud noise. The young seal, again, which was kept on board the Alexander, in one of the northern expeditions, became so much attached to its new mode of life, that after being thrown into the sea, and it had become tired of swimming at liberty, it regularly returned to the side of the beat, to be retaken on board. Such examples might be greatly multiplied; and I cannot help stating, that aware of this disposition to become familiar, and this participation in the good qualities of the dog, it is astonishing that mankind have not chosen this intellectual and finely organized quadruped, for aquatic services scarcely less important than some of those in which the dog is employed on the surface of the land.—Quarterly Journal.
Gas from Resin.
Mr. Daniel, the meteorologist, has contrived a process for generating gas from resin; which he effects by dissolving the resin in turpentine, or any other essential oil, and then allowing the fluid to drop gradually in a heated cylinder of iron.