MAN AND NATURE. 283 



it was transported in certain quantity from Britain to 

 Italy, across Gaul, by horse-carriage ; but there is no 

 memorial left of these earlier people to show that they 

 had the means either to work mines or to transport to 

 such distances the material gained. The best solution 

 is that afforded by the analogy of tin to gold. The 

 former metal, like gold, is found not only in veins with 

 a quartz matrix, but also as a surface deposit under 

 the form known as stream-tin, the outward interpreter 

 of the wealth below. This probably furnished the 

 metal to earlier ages ; existing then in larger quantity 

 than now and easily obtained ; but, like gold, exhaus- 

 tible in the end as a superficial deposit. As in the case 

 of gold, too, it is uncertain to what depth the tin-ores 

 may be found, even in the primitive veins, which give 

 earliest date to this valuable metal. 1 



Of our copper and lead mines we do not further 

 speak than by stating that they produce an aggregate 

 revenue approaching to 2,500,000/. annually. Our rock- 

 salt mines deserve some notice, not from their beauty, 

 in which they are far inferior to the mines of Wielitzka 

 and Salzburg, but from their large annual produce, in 

 different forms, of nearly a million tons of salt; and, 

 further, because we have here an illustration of that 

 human activity which is ever discovering fresh material 

 for human uses. Eock-salt has hitherto been explored 

 and worked in Cheshire only. Within the last year a 

 very deep boring for other purposes has disclosed a 

 bed of this most valuable substance in Northumber- 



1 The ancient mining implements found in Cornwall add to the pro- 

 bability that the old workings for tin there were chiefly superficial. 



