Eyc^eld Jokkul in Iceland, in December 18S1. 157 
had reached, on the 26th December, its lowest point at 28°49. 
It is a curious fact, however, that on the 8th of February the 
barometer fell to 27.25, a time when no earthquake was felt, 
and no apparent change had taken place in the eruption. On 
the 18th of February, the barometer, which had been at 29.42 
on the 11th, fell to 27.72. So late as the 23d of February, the 
Eyafjeld Jokkul emitted smoke greatly resembling the steam of 
boiling water ; and some persons were of opinion that the moun- 
tain had decreased, and was lower near the crater, as it evident- 
ly appeared to be when viewed in a direction from north to 
south. > 
It is stated that the water in the rivers that flow from the 
Jokkul and the surrounding mountains, had been considerably 
enlarged during the first day's eruption. A constant rumbling 
noise was heard in the vicinity of the volcano, attended occa- 
sionally by a dreadful crash, as if the immense masses of stones 
and ice were on the eve of being precipitated down the moun- 
tain. 
Other two volcanoes to the east, in the mountains of Kolia 
and Oraefa Jokkul, are said to have broken out, but no certain 
information has been received on the subject. 
The vessel which brought the account of the volcanic erup- 
tion to Copenhagen, left Iceland on the 7th of March ; and it is 
reported that the sailors when at sea, again saw a violent fire in 
the direction of the volcano. 
Art. XXVII. — Analysis of a Paper on the Finite Extent of 
the Atmosphere. By W^. H. Wollaston, M. D. V.P.R.S *. 
If air consist of ultimate particles, whose divisibility has a li- 
mit, an atmosphere composed of such particles must have a fi- 
nite extent, because it cannot expand beyond that distance at 
which the force of gravity upon a single particle is equal to the 
resistance arising from the repulsive force of the medium. In 
order to ascertain whether or not this is the constitution of our 
atmosphere, Dr Wollaston considers what would be the effect 
Read before the Royal Society or? the 17th January 1822. 
