105 
Ordinary Meeting, January 26th, 1869. 
R. Angus Smith, Ph.D., F.R.S., Vice-President, in the 
Chair. 
“ On Microscopical Examination of Dust,” by J. B. Dan- 
cer, F.R.A.S. 
The author stated that he had made some microscopical 
examinations of dust collected in June, July, and August 
last, and also of the particles contained in the rain water 
after the long drought. He had intended to bring these 
observations before the Society in a complete form, but 
has not hitherto found time to do so. He proposed 
to carry on observations during every month in the 
year, for the purpose of recording the average amount 
of solid matter deposited on a given area, and also as 
far as possible to ascertain the character of the deposits. 
The observations so far have shown, as might have been 
expected, that the dust in various localities, at different 
altitudes, and under other varying conditions, contained par- 
ticles differing in magnitude, appearance, and quantity for 
the same superficial area. In every instance molecular 
activity was abundant, but the animal life was very variable 
in amount, the largest number of moving organisms being 
in the dust collected at the lowest points — this was about 
five feet above the surface of the earth. This dust also 
contained the largest proportion in magnitude and quantity 
of vegetable matter. These observations also show that in 
thoroughfares where there are many animals engaged in the 
traffic, the majority of the light dust which when disturbed 
reaches the average height of five feet, or about the level of 
Proceedings — Lit. &Phil. Society. — Vol. YIII. No. 9 — Session 1868 - 9 , 
