1864. | Chemistry. 745 
of sulphate of soda existed in the plaster or in the mortar of the wall. 
The salt would aggregate together, then form ice-like crystals; would 
leave the plaster, and show itself in a bloom on the surface of the fr eScO, 
to be re-dissolved by the first moisture which came oyer it, and then 
be re-absorbed again, tiil at last it would aggregate into blotches, and 
the destruction would be complete. To preserve the fresco, the author 
recommended that the robing-room should always be kept dry and 
warm. 
Dr. C. Calvert’s paper, “On a New Method of Extracting Gold 
from Auriferous Rocks,’ described a method which presented the 
advantages of not only dispensing with the costly use of mercury, but 
also of extracting the silver and copper which the ore might contain. 
The agent employed was nascent chlorine, evolved from a mixture of 
salt and binoxide of manganese ground up with the auriferous quartz 
in the proportion of two or three per cent. When sulphuric acid was 
added the liberated chlorine would attack the gold, and upon allowing 
water to percolate through the mass it would dissolve out all the gold 
(as well as the copper and silver), which could then be easily precipi- 
tated in the metallic state. This process was said to yield good 
results, even when working upon a very poor quartz. 
Mr. F. Field then described a new ore of tin, and appended to it 
a few remarks on the state of mineralogy in this country. Referring 
to the high price and scarcityof bismuth, he said that if search were 
made in Cornwall there would be no difficulty in getting it; but some 
persons seemed to have gone fossil mad, and neglected the really valu- 
able minerals, which could be found in almost every county. 
These remarks were entirely corroborated by Mr. Salmon and 
Professor Tenant ; and the latter speaker instanced a case in Australia, 
where a black substance which was at first thrown away in the rush 
after gold was afterwards found to be tin ore, and was sold for 40/. 
a ton. 
An important paper was then read by Mr. Spence, “On Copper 
Smelting and the Means of Economizing the Sulphur evclved in the 
Operation.” He said he had for many years directed his attention to 
the subject of economizing the sulphur in copper ores. He had 
erected furnaces in which small ores could be calcined with little 
expenditure of fuel and labour, and this enabled him to send all the 
sulphur so eliminated into the vitriol chambers as sulphurous acid gas. 
The amount of sulphur wasted in copper-smelting, and which could be 
economized by the use of such calcining furnaces as he had erected 
was something enormous. It had been estimated at 70,000 tons per 
annum, which at the present price of sulphur would be worth 455,000. 
A paper by Dr. M. B. Herapath, “ On a New Method of Detecting 
Arsenic, Antimony, Sulphur, and Phosphorus by their Hydrogen Com- 
pounds when in Mixed Gases,” entering into special analytical 
details, is of too limited an interest to be transferred to our report, and 
from the nature of the subject it cannot be given in abstract. The 
same may be said of Mr. Catton’s papers “ On the Direct Conversion of 
