and for this reason the chemist should never be deterred by a great waste of time and money, if an accurate result should require extravagant means. As assaying is only an aid to technical operations, and these never can extract the whole amount of a metal or other component part contained in a composition, (be the latter a natural or artificial one,) with true chemical precision, it is selfevident that much time and labour would be unnecessarily lost, if the same attention were devoted to it as would be requisite in an analysis. This, however, also shows that it is utterly inadequate for purely scientific ends.

Assaying was the earliest known branch of chemistry, and in fact that one which afterward, through the medium of the various investigations of alchemy, drew attention to theoretical chemistry, and thus founded that science.

The art of assaying is so ancient, and it has so constantly and imperceptibly re

ceived new additions and perfections, that its origin is entirely unknown. Agricola of Saxony, who lived in the earliest half of the sixteenth century, was the first to collect the facts and write on this subject, (G. Agricola de Re Metallica, libr. XII. Basil, 1546.) Since then the manifold discoveries of more enlightened periods have vastly enlarged and developed this branch of study.

It is not by any means always necessary that the same measures be employed for these tests as are used in the separation of the single constituent from the rest of the compound in large quantities; as, for instance, in the processes of smelting and amalgamation, although, if convenient, it is very advisable, as it facilitates the metallurgist in the detection of the best fluxes and admixtures to be added to his peculiar

ores.

The assayer should be guided in his operations by chemistry, and the study of

the latter, particularly as far as regards the principal and more common substances, should never be omitted. In other respects, all that can be recommended to one who desires to perfect himself in assaying, is the most scrupulous cleanliness, order, and precision as regards his assays and implements, and the most unwearying adroitness and attention in performing the manipulations required by his science.

I.

Description of the Implements and Utensils used in the course of Assays by Heat.

AMONG the articles necessary for an assayer's office, of course the first that requires a description is the furnace. For most purposes the muffle furnace suffices, and it is the only one used for gold, silver, and copper ores; but for iron, lead, &c. we require another, though much simpler one. I shall first describe the muffle furnace, (Plate I. figs. 1, 2, and 3.) The characteristic part, the one from which this furnace derives its name, is the muffle, illustrated on the same plate, in figs. 7 and 8. Both these diagrams give a perspective view, the first a semilateral, the second one from in front. They can be procured in most of our larger cities, and are manufactured in

great quantity in Hessia, of a very firm and fire-proof siliceous clay, the same material as that used for the well-known Hessian crucibles, (Plate II. fig 5.) The one from which the drawing was taken in Plate I. measures eight inches across the bottom from mouth to back outside, and four inches down the back. The holes opening upwards towards the interior measure each an inch and a half lengthways, but their number of course varies according to the size of the muffle, which again should depend on the quantity of assays expected to be performed at once. The back and the mouth of the muffle are equal in size.

The muffle furnace is exhibited from in front in fig. 1, in a lateral section in fig. 3, and in a transverse perpendicular section in fig. 2. A scale, showing the proportionate dimensions in English feet, is attached, to facilitate the use of the drawings in building a furnace; for though very small, they have been made with much care, and, with