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Mr. Fryer stated that, with a view of ascertaining whether 
the barometer was subject to minute oscillations inappreciable 
by the ordinary method of observing, he had placed an aneroid 
barometer under the microscope, using the quarter-inch object 
glass, and, by bringing one of the striae on the surface of the 
steel index into focus, he was able, by means of the micro- 
meter, to observe a movement of the 20,000th of an inch. 
The index appeared to be in constant motion, but at present 
he was not prepared to lay any set of observations before the 
Society. Mr. Fryer also suggested, for the same purpose, 
the use of a barometer filled with the oleine of olive oil, such 
an instrument being free from the disturbances caused by the 
w'atery vapour present in the water barometer and exhibiting 
a greater range. 
PHYSICAL AND MATHEMATICAL SECTION. 
April 25th, 1861. 
Mr. Mosley read an extract from a letter received by him 
from Dr. Martin, of Lisbon, in which were enclosed a series of 
meteorological observations taken at that place, from the 6 th 
to the 12th February last, both inclusive. 
Mr. Vernon produced a printed series of meteorological 
observations made at Sydney and Paramatta, in 1857, 1858, 
and 1859, which he presented to the Section. 
Mr. Baxendell gave details of observations which he had 
made during the last few days on a large and remarkable solar 
