TRURO TO CAPE d'oR. 107 



this coast. At Cape d'Or, as at the Five Islands, a great mass of trap 

 rests on slightly inclined red sandstone, and this again on disturbed 

 Carboniferous rocks, while, behind and from beneath these last, still 

 older slates rise into mountain ridges. Cape d'Or thus forms a great 

 salient mass standing out into the bay, and separated from the old 

 slate hills behind by a valley occupied by the red sandstone and 

 Carboniferous shales. Cape d'Or differs from most of the trappean 

 masses which have been described in the arrangement of its component 

 parts. The upper part of the cliff consists of amygdaloid and tufa, 

 often of a brownish colour, while beneath is a more compact trap, 

 showing a tendency to a columnar structure. The whole forms a 

 toppling cliff, more shattered and unstable in its aspect than usual. 



Cape d'Or derives its name from the native copper which is found 

 in masses, varying from several pounds in weight down to the most 

 minute grains, in the veins and fissures which traverse the trap. It 

 is sometimes wedged into these fissures, along with a hard brown 

 jasper, or occupies the centre of narrow veins of quartz and calc spar. 

 At first sight, these masses and grains of pure copper appear to have 

 been molten into the fissures in which we find them. On more careful 

 consideration of all the circumstances, and those of the associated 

 minerals, it seems more probable that the metal has been deposited 

 from an aqueous solution of some salt of copper, in a manner similar 

 to that of the electrotype process. Why this should have occurred 

 in trap rocks more especially does not appear very obvious ; and, 

 indeed, when we take a piece of native copper from Lake Superior or 

 Cape d'Or, with the various calcareous and silicious minerals which 

 accompany it, nothing can be more difficult than to account on chemical 

 principles for these assemblages of substances, either by aqueous or 

 igneous causes. Nature's chemistry is often thus inscrutable in its 

 details, for the behaviour of substances, when brought into contact 

 with each other in the bowels of the earth, is often very different from 

 that which they display in the laboratory ; and, besides, nature's 

 processes are not limited by time, and long continued chemical actions 

 often produce effects which would hai'dly be inferred from experiments 

 which are limited for their performance to hours or days. I have, in 

 a paper on the cupriferous trap rocks of ISIaimanse in Lake Superior,* 

 shown that the native copper of that locality must also be accounted 

 for by aqueous causes. 



The copper of Cape d'Or is not likely to become of mining im- 

 portance, as it does not appear in large quantity in any one portion 

 of the mass, and this latter is itself not of very great extent. The 



* Canadian Naturalist, vol. ii. 



