The superior light of the single refraction can need no comment—and it is evident that there must be a degree of power at which that of the compounds will become too dim and feeble for vision,—while that of the single instrument will still retain a due intensity. For these reasons it is conceived that the close and penetrating scrutiny of lenses of diamond of perhaps only the 1/200th inch focus, and an equal aperture (which their very low aberration would easily admit of,) must enable us to see further into the arcana of nature than we have yet been empowered to do. Glass globules of 1/200th inch focus and indeed much deeper have been executed; but the testimony of _lenses_ of diamond would certainly be far more respectable, and is at least worthy of trial and examination.—C.R.G. [4] In Dr. Brewster’s treatise on new Philosophical instruments, Book 5, chap. 2, Page 403—Account of a new compound Microscope for objects of Natural History—is the following passage: “We cannot therefore expect any essential improvement in the single microscope, unless from the discovery of some transparent substance, which like the diamond combines a high refractive with a low dispersive power.” From which it seems certain that the Doctor never contemplated the possibility of working upon the substance of the diamond, though he must have been aware of its valuable properties. [5] There are fourteen different crystalline forms of the diamond, and of this number, from the laws which govern the polarization of light, the octohedron and truncated cube are probably the only ones that will give single vision. It is unfortunately very difficult to procure rough diamonds in this country, so we are compelled to use stones already cut, and to subject them to trial in the way mentioned in the text. [6] As many amateurs of science might take an interest in the inspection of the peculiar effect these lenses have on transmitted _light_, I shall be happy to exhibit them, as also the perfect lens. _Analysis of a newly-discovered Spring, at Stanley, near Wakefield_.—By Mr. William West.