60 Aneroid Barometers. 



It is therefore possible that gold, under certain circum- 

 stances, may, by the presence of silica in solution, become 

 disposed to combine with oxygen, and then to form with 

 the silica a silicate of gold. 



If further experiments prove that alkaline silicates favour 

 the solubility of silicate of gold, this silica theory will be 

 open to but few objections, and the difficulties to impede 

 our progress in solving this- most interesting problem in 

 chemical geology will be greatly diminished, as it will not 

 require the presence of strong chemical agents, which are 

 not to be found either in the rocks, or in the meteoric 

 waters percolating through them. 



Art. VI. — Aneroid Barometers, and, the Methods of Obtain- 

 ing their Errors. By Mr. E. L. J. Ellery, President. 



[Abstract, Read 11th May, 1868.] 



In this paper the President referred principally to the 

 construction, mode of using, and the correction of errors of 

 aneroid barometers. He pointed out the great utility of 

 these, both as scientific instruments and domestic weather- 

 glasses, as well as of their great value as marine barometers. 

 He drew attention to the absurdity of the ordinary printed 

 words on barometers, as being quite inapplicable, at all 

 events to this climate, and stated that the point marked 

 " stormy," namely twenty-eight inches, was seldom or never 

 reached in these latitudes, and that our most violent storms 

 occurred with a much higher barometer. He then gave the 

 following series of directions, for the guidance of those using 

 the barometers as a weather-glass in Melbourne and its 

 neighbourhood : 



It should always be remembered that the barometer 

 foreteils coming weather rather than indicates weather 

 that is present; that the longer the time between the 

 signs and the change foretold by them the longer 

 such altered weather will last ; and on the contrary, the less 

 the time between a warning and a change the shorter will be 

 the continuance of such predicted weather. If a barometer 

 is about at its ordinary height — near thirty inches at the sea 

 level — and is steady or rising while the thermometer falls, 

 S.W., S., and S.E. winds may be expected. On the contrary, 

 if a fall takes place with a rising thermometer, wind and 



