64 Dr. Mac CuUocli on Jasper. 



sess a considerable extent, the specimens from which that judg- 

 ment has been formed, have been merelj of an occasional nature, 

 and that the leading mass has been some other rock of which 

 certain portions assume the characters of jasper. 



It is said, indeed, to form a range of mountains in Siberia ; 

 but the testimony on this head is of such a nature as not to claim 

 much credit. It is not difficult for those who are practically ac- 

 quainted with geological investigations, to account for errors of 

 this nature, as well as for the apparent confidence with which 

 such statements are made, not merely by ordinary travellers, but 

 by geologists indulging in rapid and superficial views. It has, 

 however, been asserted on authority that cannot be questioned, 

 that it does actually occur in the country just mentioned, in very 

 large masses embedded among the primary strata. It has also 

 been observed lying in the same manner in the Apennines ; and 

 both these observations, as far as concerns the mode of its oc- 

 currence, are confirmed by similar facts in our own ; as, in 

 Scotland it is found on the southern skirts of the mountains near 

 Fettercairn with similar connexions. 



In France, according to Soulavie, it is found in a position in- 

 termediate between granite and basalt ; and although no such 

 instance has yet occurred in Britain, as far as I am aware, it is a 

 situation extremely consonant to its general habits in many other 

 cases. 



Under these circumstances, and with these doubts about the 

 care which has been applied to its examination, it has been found 

 impossible to derive from the works of such authors as I have 

 examined, any accurate geological information that could be 

 relied on. 



It must moreover be remarked that the term jasper has itself 

 been applied in so vague a manner as to lead to great confusion. 

 Being an ancient term, and having been commonly used in a 

 commercial rather than in a mineralogical sense, it often is im- 

 possible at present, without an actual sight of the specimens in 

 question, to understand what is intended in descriptions where 

 it is named. It would be a sufficient example of this laxity to 

 remark, that even the calcareous stalagmites of Sicily have gone 



