1823.] Geological Transactions of Cornwall, Vol. II. 297 



that these floors underlie four feet in six to the north-east, and 

 that they occur in a white porphyritical rock. " The famous 

 Stock-work at Altenberg (a stumbling block in the way of geo- 

 logists), is nothing else than a large mass of the mountain 

 impregnated with tinstone, occasioned by the meeting of a 

 number of lodes and veins at this point, some of these crossing 

 each other nearly at right angles, some bearing each other along 

 in their crossing, and others stretching along in a parallel or 

 nearly parallel direction. The same natural cause seems to have 

 produced, at the same period, an infinite number of smaller veins 

 and fissures, which run in all directions through the rock, so 

 that many parts of the Stock-work bear a striking resemblance, 

 on a larger scale, to the veined varieties of common marble. 

 The veins here are chiefly of quartz, and are united to the rock 

 in such a manner as to indicate their coeval formation. It is 

 remarkable, however, that the tin lies for the most part dispersed 

 through the latter, and this circumstance has given occasion to 

 the very singular mode of working the mine ; for as no profit 

 attended the driving upon regular lodes, and the mass of rock 

 was unequally impregnated with tin, the greatest degree of 

 irregularity appears to have marked the progress of the excava- 

 tions from their commencement. . . .The rock itself, which com- 

 poses the Stock- work, is a variety of porphyry, the mass being 

 a fine mixture of chlorite earth and clay, in which the grains of 

 felspar and quartz are scarcely perceptible." 



To this follows some particulars of the Stock-work at Geyer, 

 in Saxony ; and, after adverting to the probable existence of 

 similar veiniferous masses of rock in Cornwall, Mr. Hawkins 

 concludes his paper with the following advice as to the proper 

 mode of working them. 



" I would suggest the expediency of removing the whole mass 

 of impregnated rock from the surface downwards, in successive 

 terraces or levels ; most earnestly recommending the immediate 

 adoption of the Saxon process of stamping and dressing. No 

 man who has witnessed this process, can forbear reprobating 

 our own, as rude, wasteful, and inefficient ; for if, with any 

 truth, it may be said, that in the art of mining we are inferior to 

 our continental neighbours, we are so in a most shameful degree 

 in the department which I have just mentioned." 



V. On the relative Age of the Veins of Cornwall. By Joseph 

 Came, Esq. FRS. MRIA. Hon. MGS. MGSC. 



In the commencement of this extended and elaborate commu- 

 nication, after some remarks on the number and variety of the 

 mineral veins of Cornwall, and on the diversity of sentiment 

 respecting the formation of veins, Mr. Carne observes, " with 

 respect to their comparative or relative age, I apprehend all par- 

 ties (except those who hold that all veins are contemporaneous, 

 and were formed at the same time as the containing rocks), are 

 agreed on this important principle ; that a vein which is inter- 



