BOOK VII. 



INCE the Sixth Book has described the iron tools, 

 the vessels and the machines used in mines, this 

 Book will describe the methods of assaying' ores ; 

 because it is desirable to first test them in order 

 that the material mined may be advantageously 

 smelted, or that the dross may be purged away and 

 the metal made pure. Although writers have men- 

 tioned such tests, 3'et none of them have set down the 

 directions for performing them, wherefore it is no 

 wonder that those who come later have written nothing on the subject. 

 By tests of this kind miners can determine with certainty whether 

 ores contain any metal in them or not ; or if it has already been 

 indicated that the ore contains one or more metals, the tests show whether 

 it is much or little ; the miners also ascertain by such tests the method by 

 which the metal can be separated from that part of the ore devoid of it ; 

 and further, by these tests, they determine that part in which there is much 

 metal from that part in which there is little. Unless these tests have been 

 carefully applied before the metals are melted out, the ore cannot be smelted 

 without great loss to the owners, for the parts which do not easily melt in the 

 fire carry the metals off with them or consume them. In the last case, they pass 

 off with the fumes ; in the other case they are mixed with the slag and furnace 

 accretions, and in such event the owners lose the labour which they have spent 

 in preparing the furnaces and the crucibles, and further, it is necessary for them 

 to incur fresh expenditure for fluxes and other things. Metals, when they have 

 been melted out, are usually assayed in order that we may ascertain what pro- 

 portion of silver is in a centumpondium of copper or lead, or what quantity of 

 gold is in one libra of silver ; and, on the other hand, what proportion of copper 

 or lead is contained in a centumpondium of silver, or what quantity of silver is 

 contained in one libra of gold. And from this we can calculate whether it 

 will be worth while to separate the precious metals from the base metals, or 

 not. Further, a test of this kind shows whether coins are good or are 

 debased ; and readily detects silver, if the coiners have mixed more than is 

 lawful with the gold ; or copper, if the coiners have alloyed with the gold or 

 silver more of it than is allowable. I will explain all these methods with the 

 utmost care that I can. 



^We have but little record of anything which could be called " assaying " among the 

 Greeks and Romans. The fact, however, that they made constant use of the touchstone 

 (see note 37, p. 252) is sufficient proof that they were able to test the purity of gold and silver. 

 The description of the touchstone by Theophrastus contains several references to " trial " 

 by fire (see note 37, p. 252). They were adepts at metal working, and were therefore familiar 

 with melting metals on a small scale, with the smelting of silver, lead, copper, and tin 

 ores (see note i, p. 353) and with the parting of silver and lead by cupellation. Consequently, 

 it would not require m.uch of an imaginative flight to conclude that there existed some system 

 of tests of ore and metal values by fire. Apart from the statement of Theophrastus referred 

 to, the first references made to anything which might fill the role of assaying are from the 

 Alchemists, particularly Geber (prior to 1300), for they describe methods of solution, 

 precipitation, distillation, fusing in crucibles, cupellation, and of the parting of gold and silver 

 by acid and by sulphur, antimony, or cementation. However, they were not bent on 



