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On Improvements in the Apparatus for Counting the Dust Particles in the Atmosphere

Published online by Cambridge University Press:  15 September 2014

John Aitken Esq.
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Extract

In a previous communication I described the apparatus first used for counting the dust particles in the atmosphere. That apparatus was constructed of such materials as could be easily obtained ready made, and was fitted together in such a way that any one acquainted with laboratory work could easily repeat the experiments. Though that apparatus is satisfactory enough for preliminary work, and gives fairly good results, yet it is evidently not suited for regular everyday use; and, besides that, there are certain defects in it which can be avoided in apparatus specially constructed.

Type
Proceedings 1888-89
Information
Proceedings of the Royal Society of Edinburgh , Volume 16 , 1890 , pp. 135 - 172
Copyright
Copyright © Royal Society of Edinburgh 1889

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References

note * page 160 Though there was a close relation between the transparency of the air and the number of dust particles in itj during these Colmonell observations, yet it is evident that we will not be entitled to expect this relation to hold good under all conditions. The amount of vapour in the atmosphere, or rather the degree of saturation of the air, will have an effect on the size of the particles, more especially when the air is nearly saturated. We are, therefore, only entitled to expect this relation to hold good while the degree of saturation remains constant, which it probably did during these observations, the air being nearly saturated during most of the time.

note * page 170 After a considerable amount of practice with this apparatus, I find it better always to close the stopcock before drawing down the piston, even when only 1 c.c. of air is required. The graduation of the pump ought therefore to be made to show the amount of air taken out of the receiver while the stopcock is closed.

note * page 172 After a considerable experience with this apparatus, T have never found it necessary to use the smallest of the measures, even when testing the air of cities. It may, therefore, be omitted. But if retained for special reasons, the centre stopcock should be placed at an angle with the others, so that the handles may be more easily worked, than when they are all crowded in one line.