Page:Transactions and Proceedings of the New Zealand Institute - Volume 1 (2nd ed.).djvu/515

Rh the question brought by Mr. Whitaker before the notice of the members of tke Institute, it was certainly very remarkable, but he was not at all disposed to doubt it; but, taking it for granted that one water saved more gold than the other, it could only arise from one of two causes—the one chemical and the other mechanical. The two waters mentioned might be of different specific gravities. This might be a possible explanation, but he did not think it was sufficient to account for it. The water spoken of by Mr. Whitaker probably contained silica in solution. What action the silica might have upon the gold was very obscure; but still there was the fact as stated by Mr. Whitaker, and there might be some unknown action between silica, which was an acid, and gold, which might have some effect on the gold, and make it less susceptible of amalgamating with the mercury than if the water was quite clear. He only threw out these suggestions on the spur of the moment, the question having come up during the last half-hour.

2. "On the Geology of the Island of Pakihi," by Captain F. W. Hutton, F.G.S. (Transactions, p. 118.)

Captain Hutton said there were two or three things in connection with the Island of Pakihi which gave it a particular interest, one of which was, that it contained large quantities of manganese, by which they might ultimately be able to extract gold from iron pyrites, without having to roast it.

Dr. Purchas said he was aware that on that occasion he had promised to give a vivâ voce description of the various processes employed in saving gold. He had, however, no time to get up his subject as he should have wished, but would, as there was so little business on the paper, say a few words on the subject. The speaker then went on to describe the manner in which gold was treated in South America, saying that far poorer ores than those at the Thames were crushed and made payable. Speaking of the space required for the working of some of the machinery in South America, he said that on many claims a space as large as six men's ground at the Thames was required for amalgamating ground. He then briefly explained the process by which the amalgamation took place. The ore, speaking more particularly of silver ore, was laid upon the ground mixed with salt, and horses were kept going round, treading upon it, and so breaking it fine. It was also dressed three or four times with quicksilver, and, in some seasons of the year, small quantities of lime were added. It was a remarkable circumstance that in the winter the temperature was made higher and in the summer was made lower by the process. If the ore was poor in sulphur, then another ore having sulphur was mixed with it, and trodden down in it to make it work, and left on the ground, in summer