ANNIVERSARY ADDRESS OF THE PRESIDENT. Ivii 



the grains of gold are found, finer in places more remote from the 

 mountains, and coarser in creeks at their base. In these latter loca- 

 lities the gold is generally most abundant. The first diggings were 

 commenced in this range about 25 miles west of Bathurst. Gold 

 has also been found in numerous other places. Mr. Clarke calculates 

 that in this tract of the Macquarie alone it must extend over an area 

 of 700 or 800 square miles ; and this is doubtless but a small frac- 

 tion of the area throughout which it may be expected to be found 

 hereafter. 



Other metals are usually found in greatest abundance in veins 

 which are generally as rich at great depths as at the surface, and 

 sometimes more so ; but veins of gold, on the contrary, where they 

 have been worked in the solid rock, have been invariably found to 

 become poor at any considerable depth beneath the surface, so that 

 the working of them is seldom remunerative. It is the comparative 

 richness of the gold-veins near the surface which accoimts for the 

 existence of the metal in such abundance in the alluvium or Drift, 

 the same agencies which deposited the drifted materials having also 

 carried away the gold from the superficial portions of the veins in 

 which it was originally found. In Australia we have only a repeti- 

 tion of the phsenomena which have presented themselves in the IJral, 

 California, and in every other locality where gold has been found in 

 abundance. 



The next paper to which I shall call your attention, although not 

 directly on the subject of the Drift, may be considered as closely 

 associated with it, one of its principal objects being to account for 

 the peculiar climatal conditions of the glacial period — that period to 

 which geologists now universally refer the general phsenomena of • 

 Drift. I allude to the paper which I have myself brought recently 

 before you, "On the Causes of Change in the Earth's Superficial 

 Temperature." You will recollect that, until very recently, the only 

 change of climate which had been recognized by geologists as having 

 taken place during the earth's geological history was one from a 

 higher to a lower temperature, and, for those who believed in the 

 primitive heat of the globe, that heat afforded one obvious cause for 

 this higher temperature at remote geological epochs. When, how- 

 ever, an examination of the phsenomena of the glacial epoch rendered 

 it necessary to recognize a change of climate in our own region of 

 the globe from a lower temperature during that period to a higher 

 subsequent temperature, new conditions were added to the problem 

 which rendered the cause formerly assigned manifestly inadequate for 

 its solution. Two other causes, however, had been previously sug- 

 gested, which might possibly account, not only for a change from a 

 higher to a lower superficial terrestrial temperature, but also for oscil- 

 latory changes. One of these assigned causes rested on the hy- 

 potheses of motion of the whole solar system in space, and the vari- 

 able temperature of the different regions through which it might thus 

 pass ; the other cause assigned was the influence of different con- 

 figurations of land and sea on the climatal state of particular portions 

 of the earth's surface. Thus of the three causes above alluded to. 



