president's address — SECTION c. 145 



Such mining operations as have been carried out in the auriferous 

 conglomerate have been, up to the present, confined to relatively 

 shallow depths along the outcrop ; the conglomerate is in part marked 

 by the presence of large quantities of iron pyrites and its oxidation 

 products. In the unoxidised portion the pyrites occurs both as crys- 

 tals, grains, and rounded or pebble-like forms. A certain interest 

 attaches to the occurrence of these rounded pebbles and pellets of 

 auriferous pyrites and hematite on account of the fact that they have 

 been regarded as owing their shape to attrition, and that the gold and 

 the iron are detrital, having been deposited with, the pebbles of the 

 conglomerate, as the result of the disintegration of the underlying 

 auriferous rocks. The evidence respecting the origin of the gold in 

 the Nullagine conglomerates indicates that it is a secondary and not 

 an original constituent, and, further, that the primary source of the 

 gold is the quartz reefs which occur in the underlying formation. 



From the known occurrence of auriferous quartz reefs, which 

 furnished no small portion of the pebbles of certain portions of the 

 deposit, it is, of course, quite conceivable that a certain amount of 

 detrital gold forms part of the conglomerate, but there are obviously 

 no means of ascertaining what is the proportion of primary to secondary 

 gold. There seems, however, good reason for believing that by far 

 the greater bulk of the gold, together with the pyrites, was introduced 

 by solution percolating down to the most porous portions of the con- 

 glomerate, this condition being facilitated by the downward inclina- 

 tion of the bed rock, and, possibly, accenuated in part by the folding 

 which the strata have undergone. 



One of the most important advances in Western Australian geology 

 is the recognition of a glacial conglomerate in the marine Permo- 

 Carboniferous rocks, near the Tropic of Capricorn. 



The Carboniferous rocks of the State cover a wide extent of country, 

 and bid fair to become a considerable economic importance. 



The occurrence of Carboniferous rocks would seem to have first 

 been made known through Sir George (then Lieutenant) Grey, in the year 

 1841, in his " Journals of the Two Expeditions of Discovery in North- 

 western and Western Australia during the years 1837-9." There are 

 four districts in which fossiliferous Carboniferous rocks are known in the 

 State, viz. : — Kimberley, the Gascoyne, the Irwin Eiver, and the Collie 

 districts. 



The Carboniferous rocks of Kimberley have recently been investi- 

 gated by Dr. Jack, when in the quest for artesian water. This observer's 

 work was carried out in the months of December and January, during 

 one of the most severe droughts experienced in the district, and with a 

 temperature often reaching 114° Fahrenheit. Despite the fact that 

 the route followed in investigating these beds had perforce to be 

 governed by considerations of grass and water, our knowledge of the 

 Carboniferous rocks of Kimberley has been greatly extended. The 

 formation is divisible into a lower or limestone series (in which lime- 

 stones predominate), and an upper or sandstone series (made up largely 

 of sandstones and other sedimentary beds). The two series have been 



