[Plate XXXI.] Fig. 2, exhibits a view of the microscopical crystals of nitre. These shoot from the edges with very little heat, in flattish figures, of various lengths, and exceedingly transparent, the sides nearly parallel, though rather jagged, and tapering to a point; after a number of these are formed, they often dissolve under the eye, and disappear entirely; but in a little time new shoots will push out, and the process go on afresh. Beautiful ramifications are formed round the edge, and many regular figures are to be observed in different parts of the drop. Fig. 1 is the real size of the drop.
Fig. 4 is a drop of distilled verdigrise, as it appeared when viewed by the microscope. There is a difference in the appearance from this substance, according as the time of the application is nearer to, or more distant from that in which the solution was made. Fig. 3, the size of the drop.
If a drop of distilled verdigrise upon glass be viewed through the microscope, after the crystallization is completed and the water evaporated, there remains a substance round the crystallization, which preserves the original size and shape of the drop when a liquid; betwixt this verge of the drop and the crystals fine lines are discernible running from the crystals to the circumference of the drop, at various angles with the crystals; whatever direction they take, they are always perfectly straight, and of an equal thickness throughout. When the drop is viewed through a light ground, these lines appear dark; but when viewed through a dark ground, they then shine and appear of the beautiful green colour natural to the crystals of verdigrise.
[Plate XXXII.] Fig. 1, represents the microscopical appearance of the crystals of salt of wormwood. The shootings from the edges of this solution are often very thick in proportion to their length, their sides full of notches, the ends generally acute; many spear-like forms are also to be observed, as well as little crystals of a variety of figures.
Fig. 2. Salt of amber. The shootings of this salt are highly entertaining, though the process is very slow; many spiculæ shoot from the edge towards the middle of the solution, and from the pointed ends of the spiculæ a great variety of diversified branches may be observed, variously divided and subdivided, and forming at last, says Baker, a winter scene of trees without leaves.
Fig. 3. Salt of hartshorn. This salt shoots out from the edge of the drop into solid, thick, and rather opake figures; from these it often shoots into branches of a rugged appearance, similar to those of some species of coral.
Fig. 4 represents the microscopical crystals of sal ammoniac. These form a most beautiful object in the microscope; a general idea may be more easily acquired by attentively viewing the figure here exhibited, than by any verbal description.[146]
[146] A collection of salts, as recommended by Mr. Baker, properly prepared and packed in portable boxes by Messrs. Jones, the reader will see in the extensive [list] of microscopic objects now annexed to this work by the editor.