Bv this account it appears that the 
acme of lowness of the barometer oc¬ 
curred at a great distance from the 
volcano, and thence progressively near¬ 
er (in lines almost at right angles with 
the verge, the magnetic equator and 
the climates) until it reached Iceland 
on the last of the three da vs. 
A> jlvous, where die barometer was . 
at the lowest, the mercury fell to 
twenty-five and three fourths inches: 
hence the pressure of the atmosphere 
at Lyons was reduced about one 
seventh. 
The extraordinary lowness of the 
barometer above stated, w r as most pro¬ 
bably owing to the general surface of* 
the earth in Europe—including the 
sea—being somewhat elevated by an 
elastic aerial fluid existing in the mid¬ 
plane-space, a portion of which elastic 
fluid escaping progressively by means 
of the irruption of the volcano, per¬ 
mitted the surface of the earth to sub¬ 
side, by which subsidence the incum¬ 
bent pressure on the barometer tem¬ 
porarily lessened. 
Why a subsidence of the crust should 
lessen the incumbent pressure, may be 
questioned; but, if it be admitted that 
there is another sphere of some sort 
(whether it be constituted of solids or 
of compacted fluids is not material) 
over our heads, as there are many 
reasons to believe there is, the above 
will no longer be a questionable con¬ 
clusion, but a very natural one. 
Perhaps the sphere, with its equa¬ 
tors, may be exemplified by turning in 
a lathe a hollow sphere with open 
pole^ and delineating thereon a true 
equatorial belt equidistant from the 
verges, to represent the magnetic 
equator, and also marking the climates 
equidistant from each other, between 
