Retrospect of Philosophical, Mechanical, Chemical and Agricultural Discoveries (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1812 Excerpt: ...the manufacturers in their choice of the best samples. 1. Colour. The colour of pure tin is a brilliant white, nearly approaching that of silver. When the tin is alloyed with any notable proportion of iron, copper, or lead, the colour of the mixture tends more or less to grey. Arsenic, on the contrary, increases its whiteness and brilliancy, but at the same time makes it harder. 2. Fracture. Take a rod of tin, cut it half through with a chisel, and then bend it hackwards and forwards till it breaks. If the metal is pure, it will bear repeated bending, and when at length it breaks, the two fractured ends will approach more or less to points, their grain will je as it were pasty, and the colour a dead white. If lead, or especially copper, iron, or arsenic, have been mixed wiib the tin, the fracture will take place very speedily, and the broken surface will be of a grey colour and a granular texture. Another infallible proof of the goodness of tin, is to melt a portion, and pour it into a metallic mould. The ingot thus produced will be superficially of the colour of mercury, if pure; but if alloyed with lead, copper, or iron, it will be of a dead white, or at least spotted, and the spots will appear to be a mass of minute confused crystallization. On the Geology of the West Indian Islands. By M. Cortes.--Journ. de Phys. tome 70. The islands of the West Indian sea may be divided into four classes. The first comprehends those, the surface of which is entirely calcareous: to which belong Marigalante, la Deseada, Curaccao, Bonaire, and in general all those islands, islets, and reefs of small elevation. Under the second class are included those islands which are purely volcanic, such as Grenada, St. Vincents, St. Lucie, Martinique, Dominica, the Saintes, Montserrat...