96 
The President said that he had a few small facts to bring forward — 
as he thought it a pity that any should be lost, though it was difficult to 
estimate rightly the value of small observations. The first was the pro- 
duction of pure silica on a large scale, as a by-product in the manufacture 
of super-phosphate of lime. This substance was produced by acting upon 
coprolites, which were practically fossil bones, by sulphuric acid. It had 
been often noticed that a very offensive odour was given off during the 
process, accompanied by the deposit of a white substance. Investigation 
showed that the vapour was that of hydrofluosilicic acid, from the fluorine 
in the coprolites, in which there was a greater percentage of that element 
than in ordinary bones, and that the white deposit was pure amorphous 
silica, resulting from the decomposition of the acid. 
The second fact v»as the accidental formation of crystals of iron 
pyrites. Some iron pots used in the sublimation of chloride of ammonium 
had been thrown out of use for a few weeks, and at the end of that time, 
in the interstices of the brick and clay surrounding them, were found these 
crystals. Sulphate, and chloride, of ammonium, had been heated with 
charcoal in these iron pans, and the mutual reaction of these substances 
had produced this effect. 
A specimen of superphosphate of lime was shown, apparently quite dry, 
which became pasty and almost liquid, when an attempt was made to 
powder it. An explanation of the cause of this was sought. 
Mr. W. L. Carpenter exhibited a series of very beautiful photographs 
of Swiss scenery by Braun, chiefly taken in the Bernese Oberland and the 
district immediately East of it. 
Mr. Beattie stated that he had been able to keep a wet collodion 
plate sufficiently moist for use for eight hours by adding glycerine to a 
neutral bath, or to one slightly acidified by acetic acid. His formula was 
1 oz. of pure glycerine, 1 oz. of water, 1 oz. of a ,30 grain solution of 
nitrate of silver. He also said that the result of many observations led 
him to believe that the use of decomposed fixing solution, rather than 
imperfect washing, was the cause of the fading of photographs. 
ZOOLOGICAL SECTION. 
Thursday, December 13th. — Dr. H. Fripp, President of the 
section, in the chair. 
Mr. S. Barton exhibited a rare and remarkable Coleopterous insect 
from Natal, and a specimen, preserved in spirit, of the Phalanger. or 
Australian (so-called) opossum, taken from the pouch of a female which he 
had shot. 
The President exhibited microscopic preparations of a peculiar Acarus 
found in a box of bran from the West Indies, remarkable for its curious 
jaws, adapted for crushing, and for its four pair of legs. It bad probably 
been a parasite on corn. 
