52 report — 1865. 



lities, and the schist3 containing Calceola sandalina, are evident equivalents of 

 the Eifel limestone, although the number of fossil species in these Devonshire lime- 

 stones is not nearly so great as in the Eifel. 



3. Goniatite and Clymenia-beds. — This uppermost group of the Devonian series 

 is of a more varied mineralogical composition than the two other groups ; Goniatites 

 and Clymenise are the most characteristic fossil types. On the left bank of the 

 Rhine, 'in the neighbourhood of Aix-la-Chapelle and Stolberg, the uppermost part 

 of this group is formed by schists which abound with Spirifcr Vemeuilii (Sp. dis- 

 junctus). Iu that same country these uppermost Devonian strata are immediately 

 and conformably overlaid by the true Carboniferous or mountain limestone, cha- 

 racterized by the well-known forms of Productus, as Prod, semireticulatus and Prod. 

 Cora. Dr. Romer concluded his remarks by observing that, although the present 

 more exact knowledge of the Devonian rocks in the Rhenish country was the result 

 of the labours of German geologists, it ought not to be forgotten that many years ago 

 Murchison and Sedgwick, assisted in the pakeontological department by E. de Ver- 

 neuil, recognized in the Eifel limestones an equivalent of the limestone of Torquay, 

 and so were the first who proved the existence of Devonian rocks on the Rhine. 



The President, in commenting upon the great value of the large map of "Von 

 Dechen, assured the Section that he had personally tested its accuracy in several 

 explorations of the Rhenish Provinces of Prussia, and he rejoiced to find that 

 whilst Principal Dawson had detailed the characters of the Devonian rocks of North 

 America, his friend II. von Dechen and Ferdinand Rbmer had admirably developed 

 that triple division of these rocks into which he, in his last edition of ' Siluria,' had 

 correlated with the Old Red Sandstone of Scotland, and its equivalent group as it 

 exists in Devonshire. 



On the Existence of Gold-hearing Eruptive Rods in South America wJilch 



have made their appearance at two very distinct Geological periods. By 



David Forbes, F.R.S., 4x. 



The author believed that the gold deposits of South America had not as yet 

 been studied with a view to determine the geological period at which the gold 

 itself had made its appearance. The present communication was the result of ob- 

 servations made during seven years' travels over a large part of South America, and 

 which had enabled him to class all the deposits of gold which he had visited under 

 two heads, both of which could be traced back directly or indirectly to the intrusion 

 or eruption of igneous rocks. 



Under the first head belonged all gold derived from the disintegration of granitic 

 rocks of an age later than much, if not of all of the Silurian strata, but probably not 

 later than the Devonian period. 



The largest gold washings of South America, and probably of the whole world, 

 he looked°upon as derived from this source as well as the auriferous quartz veins, 

 as these could be traced to the proximity of the granite, and which he believed to 

 have originated in, or been injected from the granite into the neighbouring strata, 

 carrying°the gold, which was 'a normal constituent of the granite itself, along with 

 it. This granite, wherever met with, is invariably auriferous in itself; and although 

 it would not pay to grind down granite mountains and wash out the gold in it, yet 

 in many parts of South America, in Brazil, near Valparaiso, &c, the granite, appa- 

 rently solid, was frequently decomposed in situ to depths of even over 200 feet, as 

 shown frequently in the late railway-cuttings, and then it sometimes^ repaid the 

 labour of washing the whole mass for the sake of the gold in it. To this class also 

 belongs several metallic veins, injected also from the granite into the neighbouring 

 Silurian strata, which contain gold, and are remarkable for the presence of other 

 minerals very characteristic, as oxide and sulphides of tin, iron pyrites, copper py- 

 rites, compounds of bismuth, tellurium, selenium, &c, many of which are seldom 

 or never met with in later rocks. 



The second appearance of gold is, however, totally distinct from the above in 

 mineral character as well as in geological age, and results from the eruption of 

 dioritic (greenstone) rocks composed of hornblende and felspar (without quartz), 



