KE. H. Davison—Primary Zones of Cornish Lodes, 505 
of the last tooth and part of the arrangement for pushing it up into 
a working position in the absence of pressure from behind. 
Mr. Adams (loc. cit., p. 121), describing a much detrited last lower 
molar in the Woodwardian Museum, says: “‘ The fangs had become 
consolidated into a ridge like the keel of a vessel ’’—an exactly 
similar condition to that here displayed. This character may thus 
be taken as confirming the conclusion otherwise arrived at that this 
is an ultimate molar. For a microscopic examination of the sub- 
stance of the keel the writer is indebted to Mr. W. Courtney Lyne, 
who identifies it as dentine, which normally composes the fangs. 
Compared with lest lower molars of the mammoth described by 
Mr. Adams (loc. cit.), and with the fragments in the Birmingham 
University Geological Museum, this is rather a narrow tooth, but the 
measures of several narrower are given in the work referred to. On 
the other hand, judging by what remains, it would, when complete, 
be fully as long as the complete molars there described, but these 
from their very completeness are probably for the most part smaller 
than the average. It is, indeed, by no means as large in any 
dimension as they often attain. 
The tooth is in a good state of preservation, the grinding surface, 
though much cracked, preserving the original relief and a fair degree 
of polish on the enamel. But at the sides of the crown the cement 
has in places fallen away as has also dentine from the keel. It 
exhibits no effects of water-wear and so cannot have been carried 
by water far from the mandible and the skull. There is every 
probability, therefore, of more mammoth remains having been 
entombed in the neighbouring gravel. 
The tooth is in the possession of Mr. Harrison’s widow, to whom the 
writer is deeply indebted for an extended loan of the specimen and 
for information regarding the position of the find. 
EXPLANATION OF PLATE X. 
Photegraph of ultimate right lower Molar cf Mammoth found at North 
Wocdchester, near Stroud, by the late Mr. W. Harrison, of Selly Oak, 
Birmingham, Easter, 1916. Photo—half natural size. 
The Primary Zones of Cornish Lodes 
By Es El. DAVISON, Buses, EVG.s. 
pas G the last two and a half years I have been engaged in 
the study of the Cornish Veinstones in the field and in the 
laboratory by microscopic and other methods, and have come to 
the following conclusions :-- 
That, as recognized by many observers, the primary minerals 
of Cornish lodes occur in zones which change their character in 
depth; thus copper minerals give place to cassiterite on passing 
down the lode and chlorite gives place to tourmaline. 
From observations on over 150 lodes in more than 100 different 
mines, taken on the spot or abstracted from old records, in and 
