4 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
Perhaps nothing could better show the objectionable character of the term 
contemporaneous than JAMESON’S statement that “serpentine contains contem- 
poraneous veins of asbest, talc, steatite, and lithomarge.” 
In Jukes’ “ Manual of Geology” the name is confined to their occurrence 
in intrusive rocks, but the above quotations from JAMESON will show that the 
word orginally had a much wider application. The authors of the most recent 
edition of this work propose to “retain the name for the purpose of expressing 
that the veins belong to the same intrusion as the masses which contain them.” 
While the very name of vein is objectionable, there is little hope of setting it 
aside, or, sooth to say, of getting a more fitting word from our own language; but 
it is the adjective to which strong exception must be taken, if contemporaneous 
is held to be at all synonymous with simultaneous. It is more than difficult to 
conceive of any one of the structures to which the term has been applied being 
paragenetic in time with the rock-masses in which it is imbedded. 
Of such of these structures as occur in volcanic rocks, we read in JUKES’ 
“ Geology :”— 
“They seem in certain cases to have been produced from some movement of the whole 
mass during consolidation, whereby yet fluid portions were injected aie cracks or 
between divisional planes of the mass. 
“In other instances, where they are found to merge into the surrounding rock along both 
their bounding surfaces, they rather suggest the idea of segregation and crystallisation 
of the mineral along particular lines.” 
The former of these modes of accounting for their formation is certainly 
adequate to explain the mode of fillg up of crevasses,—especially volcanic 
rents,—in lava streams or other plastic igneous rocks; while the second may 
suffice for rectilinear, though hardly for branching or angularly tortuous veins : 
but it is evident that the above explanations are intended to be restricted 
to veins in igneous rocks; and as regards their occurrence in metamorphic 
rocks, where they are not only immensely more numerous, but very much 
more important as bearing upon the nature of metamorphism itself, no such 
modes of explanation can meet the facts of the case. 
Putting out of consideration, meanwhile, the granitic bands or layers of 
hornblendic gneiss, and also the intrusive dykes which cut and ramify through- 
out them, we observe of these so-called contemporaneous veins, where they 
show themselves in their extraordinary development in the grey granite of 
Aberdeenshire, that they present three features which are unvarying :— 
First,—That though their course may be in the main tortuous or curving, 
it, if followed sufficiently far, will suddenly become angular and zig-zag ; as 
if, though the general solidity and cohesion of the rock mass was only such 
as to enable it to rend by tearing, it in certain of its parts was so rigid that 
it had been cracked or split. 
