Philosophical Transactions. 169 
Mr. Ivory considers in the second place the differential equa- 
tion that takes place at the surface of a spheroid, and the 
demonstrations which have been published by Laplace and by 
Poisson ; and he concludes that this equation “ is wanted 
neither for proving the possibility of the developement, nor for 
calculating its terms. But in this plainer way of considering 
the matter,” he proceeds, “ it appears that the developement 
does not represent the given expression when that expression 
is not an explicit function of three rectangular co-ordinates, in 
the same sense that it does, when it zs such a function. There 
is therefore a difficulty left unexplained; and we may be per- 
mitted to doubt, whether so important a part of the celestial 
mechanics, as that regarding the figure of the planets, rests with 
sufficient evidence on the doctrine laid down concerning the 
generality of the developement.” 
13. On the late extraordinary Depression of the Barometer. 
By Luke Howard, Esq., F.R.S. 
The object of this short paper is to record the remarkable 
fall of the barometer in December, 1821. On the evening of 
the 24th of that month, Mr. Howard’s barometer at Tottenham 
fell to 28.20 inches, the wind being moderate at south-east, 
with steady rain, and the thermometer in the open air standing 
at eight in the evening at 45°. At five o’clock on the morning 
of the 25th the barometer fell to 27.83 inches ; at eight o’clock 
it rose to 28 inches, and at eight in the evening to 28.40. 
In the early morning of the 27th, not having yet reached 29 in., it turned 
to fall again, with the wind at S. and S.W., after S.E.: we had again some 
heavy rain with hail about noon, and by midnight the quicksilver reached 
28.07, or .06 in., whereit stood, or rather made minute oscillations, during 
the 12 hours following, a thing I should scarcely have thought possible in 
our climate. 
At noon on the 29th the barometer began to ascend, and on 
the 31st it reached 30 inches. 
The rain for the two months of November and December, 
1821, amounted to 10.10 inches, a quantity without any re- 
corded precedent in the same space of time in London. 
Amore experienced and skilful meteorologist than Mr. Howard 
we do not know; his work on the climate of London testifies 
his persevering industry and accurate observation; the conclu- 
sion of his paper therefore we take the liberty of transcribing, 
as a lesson to all prognosticators of the weather. 1 am almost at 
a loss foran apology to the Society, for having in my last paper anticipated, 
on the strength of a single analogy, a dry year for 1821, the fact being, 
that there has fallen at Tottenham, in the whole year, no less than 33.84 
inches. It seems as if, with all our anxiety to pass the stream of uncer- 
tainty in this science, we must give over making the wooden bridges of 
conjecture, and wait till we can accumulate more solid materials. 
