Page:Proceedings of the Royal Society of London Vol 2.djvu/75

Rh employed, were now injected into the circulation of a dog. He instantly lost all power of motion; the breathing became slow, the pulse hardly to be felt. In ten minutes it was 84; in twenty minutes at 60; in an hour at 115, with the respiration so quick as scarcely to be counted. In two hours the pulse was 150, and very weak. In the mean time the animal was purged; and he vomited, first a bilious fluid, and then bloody mucus; and after lingering in an extremely languid state five hours, expired.

On dissection, the internal coat of the stomach and intestines were found inflamed in a greater or lesser degree universally.

The facts here adduced, says the author, go as far as it is possible to prove that the action of Colchicum autumnale on the different parts of the body is through the medium of the circulation, and not in consequence of its immediate effects on the stomach.

On the Cutting Diamond.By William Hyde Wollaston, M .D. Sec.R.S.Read May 2, 1816.[''Phil. Trans''. 1816, p. 265.]The author, having never met with any satisfactory explanation of the property which the diamond possesses of cutting glass, has endeavoured, by experiment, to determine the conditions necessary for this effect, and the mode in which it is produced. The diamonds chosen for this purpose are naturally crystallized, with curved surfaces, so that the edges are also curvilinear. In order to cut glass, a diamond of this form requires to be so placed that the surface of the glass is a tangent to a curvilinear edge, and equally inclined laterally to the two adjacent surfaces of the diamond. Under these circumstances the parts of the glass to which the diamond is applied are forced asunder, as by an obtuse wedge, to a most minute distance, without being removed; so that a superficial and continuous crack is made from one end of the intended cut to the other. After this, any small force applied to one extremity is sufficient to extend this crack through the whole substance, and successively across the whole breadth of the glass. For since the strain at each instant in the progress of the crack is confined nearly to a mathematical point at the bottom of the fissure, the effort necessary for carrying it through is proportionally small.

The author found by trial that the cut caused by the mere passage of the diamond need not penetrate so much as th of an inch.

He found also that other mineral bodies recently ground into the same form are also capable of cutting glass, although they cannot long retain the power, from want of the requisite hardness.



This mass was first discovered in the year 1784 by a person of the name of Bernardino da Mota Botelho, while looking after his cattle;