C 89 3 
XI. On the finite extent of the Atmosphere. By William 
Hyde Wollaston, M. D. V. P. R. S. 
Read January 17, 1822. 
The passage of Venus very near the sun in superior con- 
junction in the month of May last, having presented an 
opportunity of examining whether any appearance of a solar 
atmosphere could be discerned, I am in hopes that the result 
of my endeavours, together with the views which induced me 
to undertake the inquiry, may be found deserving of a place 
in the Philosophical Transactions. 
If we attempt to estimate the probable height to which the 
earth’s atmosphere extends, no phenomenon caused by its re- 
fractive power in directions at which we can view it, or by 
reflection from vapours that are suspended in it, will enable 
us to decide this question. 
From the law of its elasticity, which prevails within cer- 
tain limits, we know the degrees of rarity corresponding to 
different elevations from the earth’s surface; and if we admit 
that air has been rarefied so as to sustain only -j— of an inch 
barometrical pressure, and that this measure has afforded a 
true estimate of its rarity, we should infer from the law, that 
it extends to the height of forty miles, with properties yet un- 
impaired by extreme rarefaction. Beyond this limit we are 
left to conjectures founded on the supposed divisibility of 
matter : and if this be infinite, so also must be the extent of 
N 
MDCCCXXII. 
