MR. HUDSON’S HOURLY OBSERVATIONS ON THE BAROMETER. 593 
granted me, I shall be allowed to make between the Royal Society’s Standard, 
and the Mountain Barometers actually employed in those observations, and 
which are now deposited at the Admiralty. The barometer also just received 
from Germany, and made under the direction of Professor Schumacher, at the 
request of the Royal Society, by Buzengeiger of Tubingen ; and the baro- 
meter now in progress for the Society, under the direction of Dr. Prout and 
Professor Daniell, will, along with observations made both at home and 
abroad, furnish interesting data for future comparison. 
In the present communication, I have laid before the Society the results of 
a classification of my observations according to the place of the sun ; — on a 
future occasion, I propose to add those derived from arrangements made in 
reference to the position of the moon. I have also in this part of my paper 
presented data for investigating the constant horary oscillation of the baro- 
meter, and I hope to be enabled on a future occasion to submit to the Society 
the requisite data for examining the diurnal, monthly, and annual variations 
of that instrument, as well as to deduce results from inquiries made into the 
laws and nature of the ordinary and inconstant fluctuations exhibited by the 
mercurial column. 
Mr. Daniell having ascertained the deterioration of barometers in conse- 
quence of the insinuation of air between the glass and mercury into the va- 
cuum, it became imperative upon me to ascertain if possible whether the Royal 
Society’s Standard had become injured from this cause, and whether the results 
obtained from the observations made with it differed practically and in sensible 
amount, from those made with Mr. Daniell’s Mountain Barometer, an instru- 
ment considered by him as almost perfect, or with an instrument like the 
Water Barometer, widely distinct in its nature and in the corrections required 
for its reduction. I therefore carefully observed these three instruments simul- 
taneously for 360 successive hours ; and their results, already detailed, do not 
appear to differ essentially from each other in reference to the general accuracy 
of the Standard Barometer. The variations are nearly the same in amount as 
those of the Water Barometer, and both these and the mean of the observa- 
tions, in reference to the Mountain Barometer, appear to be too nearly iden- 
tical to allow of the supposition of a deterioration to any extent having taken 
place in the Standard Barometer. The two mercurial barometers give a dif- 
