Mr, William Phillips on the Vems of Cornwall. 143 



are national institutions for the education of those intended to con- 

 duct the working of mines, in the three important branches of 

 science before alluded to, and which are so intimately connected 

 with their occupation, in this country all is left to accident, and 

 the rich gifts which nature has bestowed upon us, are consequently 

 often neglected, or lavishly thrown away. 



The ores of copper, as sold at the mine, though some of them 

 are richer, do not in most instances contain more than one-twelfth 

 of copper, frequently not one-fifteenth, some of them not one- 

 twentieth. The accompanying substances are a heterogeneous 

 mixture of earths and metals, amongst which arseniates of various 

 kinds often bear a considerable proportion. It needs not to be In- 

 sisted upon that much attention ought to be given to free copper 

 from arsenic, which is so very liable to render It brittle. When a 

 pound or two of the ore is given to the sample-trier, as a fair sample 

 of 50 or 100 tons, his report is but too often grounded on the 

 weight of the prill he has obtained from a given quantity of the 

 ore, without reference to the substances with which it may be al- 

 loyed, which indeed his skill does not enable him to detect. When 

 the ore is taken from the mine, it is for the most part deposited, not 

 that of each mine separately, but mixed with that of many others, 

 without regard to the great difference that must of course exist in 

 the ore of veins, circumstanced so variously as are those of Corn- 

 wall.* And strange as it may seem, it is notwithstanding true, that 

 even the interest of the buyer seldom tempts him to swerve from 



* In reply to this observafion, it has been said that the ores of some mines are found 

 to smelt more casiiy when mingled with those of certain other mines than alone. This 

 will not perhaps be doubted. All that is now contended against is, the common 

 practice of mixing indiscriminately ores of copper of any, or rather of every dc- 

 scription. 



