542 
ZOOLOGY OF NORTH AMERICA. 
some are imbedded portions of the slate 
rocks. Granite must have been protrud- 
ed last of all the rocks, as it cuts off the 
greenstone in many places ; but the 
phenomena of the veins are still more 
singular, as first the elvans, and then 
the lodes, cut through everything. He 
referred to certain faults in the green- 
stand district of Blackdown, and, most 
singular to relate, these faults exactly 
corresponded in direction with those of 
Cornwall, although the latter were high- 
ly metalliferous veins, while the former 
were fissures destitute of any valuable 
content. He therefore laid out the con- 
ditions of a profitable metalliferous vein, 
as deduced from the experience of prac- 
tical miners, that it should be near the 
granite, and that the best signs were an 
elvan and a cross course. In the parish 
of St. Just these phenomena are in the 
highest degree remarkable ; and, near 
Penzance, where the elvan courses are 
traversed, metals are sure to occur. 
The lodes of slate rocks are generally 
unproductive. Mr. De la Beche was 
particularly anxious to impress these 
facts on the public in general, as 
mining speculations had been of late 
so much the rage, that the more theore- 
tical knowledge that could be diffused 
the better, so as to cause inquiry to be 
made respecting the geology of the mi- 
ning district about to be entered upon by 
a joint stock company, before capital was 
invested in a hazardous, and perhaps 
ruinous enterprise. 
Mr. Hopkins was called upon to make 
some observations regarding the direc- 
tion of the fissures mentioned by Mr. 
De la Beche, but he did not enter very 
fully into any discussion, as he proposed, 
on the following day, to bring the gene- 
ral consideration of fissures before the 
Section. He observed, however, that 
there must have been one great axis of 
disturbance, to which the smaller fis- 
sures must either have been parallel, or 
have circulated around it — indeed, Mr. 
De la Beche had supposed the great 
line of fissures from Blackdowm to Corn- 
wall had been curved by the intervening 
granites. He stated, that there must be 
a connexion between the width of lodes 
and their mineral contents — also, that 
in the production of fissures there must 
have been several periods of elevation. 
Mr. Fox then mentioned a remarka- 
able experiment which he had made 
upon the yellow sulphuret of copper. 
having changed it by electricity into the 
grey sulphuret. In a trough a mass of 
clay was placed, so as to divide it into 
two portions, in one of which was sul- 
phate of copper in solution, in the other 
dilute sulphuric acid. On the electric 
communication being made by placing 
the yellow sulphuret in the solution, and 
a piece of zinc in the acid, the change of 
sulphuret took place, and crystals of 
native copper were also formed up- 
on it. — Mr. Taylor bore testimony to 
the importance of geological informa- 
tion to mining agents, who now were 
informing themselves, not only in prac- 
tice, but in theory. He spoke of the 
exertions of the late Mr. Phillips in 
drawing up a geological map of Corn- 
wall, so far back as 1800. He suggested 
the propriety of tracing the lines of fis- 
sures into the coal districts, and also 
wished the directions of the lead lodes 
of the mountain limestone to be ascer- 
tained, as likely to lead to general re- 
sults — Messrs. Conybeare and Sedg- 
wick made some observations on the 
importance of maling use in Geology 
of such an agent as Electro-Magnetism. 
Section D — ZOOLOGY AND 
BOTANY. 
Professor Henslow in the chair. — Dr. 
Richardson resumed the reading of his 
Report on the Zoology of North Ame- 
rica. In touching upon the geographi- 
cal distribution of the mammalia, he 
remarked the great similarity which 
existed between them and the European 
species; whilst there was the greatest 
dissimilarity to those of South America. 
The boundary line separating the Fanas 
of North and South America, was not 
at the Isthmus of Darien, but at the 
tropic of Cancer. No Quadrumana 
occur to the north of the Isthmus of 
Darien ; though in Europe there is a 
species which ranges as far north as the 
rock of Gibraltar, in latitude 36®. 
In the order Carnivora, and family 
Cheiroptera, all the North American 
species belong to that tribe which pos- 
sesses only one bony phalanx in the 
index, and two in each of the other 
finger, to which tribe also all the Euro- 
pean bats belong, except an Italian 
speices of Dinops. None of the sixteen 
speceis recorded as natives of North 
America have been found elsewhere; 
two only have been traced over any 
great extent of country, and one of 
