GEOLOGY. 323 



advanced the idea that the pebbles, though hard and rounded when the con- 

 glomeration was effected, had since been softened, and while so, were flat- 

 tened by lateral pressure. 



Prof. Andrews, of Marietta, Ohio, had visited the spot, and was satisfied 

 that the pebbles had been fused, and not elongated by lateral pressure. 



Prof. Hitchcock said that the view presented by Prof. Andrews was for- 

 merly his own ; but he thought the weight of evidence in favor of his pres- 

 ent theory. 



Wisconsin "Potash Kettles." - Prof. Charles Whittlesey, in a paper read 

 before the American Scientific Association, 1859, stated that along the sum- 

 mit or dividing ridge between the waters of Rock River and those of Lake 

 Michigan, there are numberless crater-like depressions in the drift materials, 

 which are called by the people "potash kettles." They are in the form of 

 cavities, sunk below the general surface ten, fifteen, and even one hundred 

 feet, their outline rudely circular, and their sides as steep as the earth will 

 stand. They have been traced about a hundred miles. The materials in 

 which they are found are the coarse drift. They seldom contain water; 

 boulders are found in and around them. In the southern part of the state, 

 timber grows in them. 



While exploring the state, in 1849, it occurred to him that these cavities 

 cannot be explained by the usual and well-known examples of aqueous 

 deposits. Terraces and oblong ridges of sand and gravel might be formed 

 b} r currents and eddies acting on loose material; but these are depressions 

 on an even surface. As explanatory of the matter, he would suggest that 

 the phenomena was understood on the supposition that it was owing to gla- 

 cial action. 



On the Gold Deposits of Australia. Mr. Selwyn, director of the geological 

 survey of Victoria, Australia, in a letter recently read before the Royal Geo- 

 logical Society (London), stated that the auriferous quartz veins of Victoria 

 appeared to be as rich in gold, at a depth of 200, 230, and 400 feet, as at the 

 surface ; but that certainly the large size of the nuggets found in the gold- 

 drifts, contrasted with that of the nuggets found in the quartz-veins, seems 

 to prove that the now worn away upper parts of the veins were probably 

 richer than the lower and now remaining portions. Mr. Selwyn, according 

 to his observations, thinks that none of the gold-drifts are older than the 

 Pliocene age. Miocene and Eocene tertiaries have been recognized in Vic- 

 toria, and some probably chalk fossils have also been found. 



Hydraulic Mining in Georgia. Within the past year the gold placers in 

 northern Georgia have attracted considerable attention, and two or more 

 extensive canals or ditches have been constructed to convey water to them, 

 at an elevation sufficient to wash out the gold, by the "California hydraulic 

 method. These placers have been examined and reported on by Mr. Wm. 

 P. Blake and Dr. Charles T. Jackson. The aqueduct from the Yahoola 

 River is about twelve miles long, and to take the water across a valley near 

 Dahlinega, a trestle 240 feet high, and about 1 500 feet long, is required. A 

 notice of the placers, and the improved methods of working them, was 

 presented at the meeting of the American Association, by Mr. Blake. 



On the occurrence of Diamonds in Georgia. Prof. C. U. Shepard, in a 

 communication to Silliman's Journal, Jan. 1859, descriptive of a locality of 

 Lazulite, in Lincoln County, Georgia, calls attention to the resemblance of 

 the rock at this point (itacolumnite, and a hematitic mixture of cyanite and 

 quartz) to the diamond gangue of Brazil. Prof. S. also states that he was 



