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._