28 Notices of Memoirs—Dr. R. F. Scharff— 
tourmaline, to the various types of normal fissure-veins, where ‘it 
is associated with sulphides of iron, copper, and antimony, and to 
a lesser extent with lead. Throughout the sulphide zones it con- 
stantly accompanies gold. This association of tungsten with gold is 
one of the most significant facts in the occurrence of tungsten-ores. 
Mention should here be made of the occurrence of strings of gold in 
alluvial wolframite in the Ballinvalley stream, co. Wicklow, Ireland,* 
but it is possible that the gold has here been deposited on the wolfram 
by secondary action in the auriferous alluvium. 
It follows that tungsten, which is found in such a continuous series 
of vein-types, must give important evidence as to the ultimate source 
of the metals with which it is associated, and since tungsten is 
universally a product of the acid and superacid phases of magma- 
differentiation in the first place, it seems probable that it is to these 
magmatic phases that we must look for the ultimate point of departure 
of many gold- and sulphide-ores, just as in the case of tin-ores. 
While this line of evidence as to the source of gold-ores—especially 
when taken in conjunction with the authentic occurrences of primary 
free gold in granitic rocks—supports in part the hypothesis of 
Mr. J. E. Spurr,’ it is clear that the genesis of gold-ores and sulphides 
is much too complex to be thus dealt with. While magmatic 
differentiation has probably been the fundamental factor at work, 
there are many gold-ores which have probably originated during an 
intermediate or basic phase of differentiation. 
Apart from the view of derivation of ores by progressive magmatic 
differentiation, which is strongly supported by the evidence here 
discussed, there remains the problem of the origin of the vein- 
solutions. The view advocated by Mr. Spurr, that the quartz gangue 
of normal fissure-veins represents the extreme product of siliceous 
magmatic differentiation, seems to be of very limited application. 
' The views as to the origin of vein-forming solutions are still somewhat 
conflicting, but it is doubtful if any theory of vein-formation can be 
comprehensive which demands the exclusive agency of ‘ juvenile 
waters’, and which fails to recognize the work of underground 
solutions of meteoric origin in the middle and higher zones of ore- 
deposition. 
The work in connexion with this paper was carried out at the 
Imperial College of Science and Technology, London, and the writer 
is indebted to Professor W. W. Watts for advice and criticism. 
NOTICES OF MEMOTRS. 
On tHE Evipences oF A Former LAND-BRIDGE BETWEEN NortHERN 
Evrore and Norra America.? By R. F. Scuarrr, Ph.D., M.R.LA. 
(\HE author enunciated the theory some years ago that North-Western 
Europe and North-Eastern America had been connected with one 
another by land within comparatively recent geological times, and 
1 Bull. Imp. Inst., 1909, vii, No. 2, p. 171. 
2 Ee. Geol., ii, No. 8, p. 781. : 
3 From the Proceedings of the Royal Irish Academy, 1909, vol. xxviii, Section B. 
