592 MR. HUDSON’S HOURLY OBSERVATIONS ON THE BAROMETER. 
servations were reduced. From Dr. Prout’s experiment also just named, 
these Tables of Professor Schumacher, which he employed on that occasion, 
appear to be rigidly correct.—With respect to the third subject of investi¬ 
gation, the influence of the diameter of the tube, I am again indebted to the 
liberality of Mr. Dollond, who has, at his own expense, fitted up for my use 
a compound barometer, consisting of six tubes of different internal diameters, 
from 0T3 to 0’50 of an inch, all standing in the same cistern, and the heights 
read oft' by an index and scale common to them all. This instrument has 
already furnished some new and interesting results, and I hope to be able 
to make, and present to the Society, a complete series of observations by 
its means.—The fourth subject of inquiry, the connexion between the mag¬ 
netic and barometrical variation, has been delayed, in consequence of the 
variation needles with which Mr. Dollond intended also to supply me, 
having, from the peculiarity of their construction, presented unusual ano¬ 
malies, which he is at present investigating. When these magnetic needles 
are completed, the series of observations which I propose to make with 
them, will be rendered more interesting and valuable by the simultaneous 
observations, both on them and on the barometer, which Captain Smyth 
has kindly undertaken to make at his Observatory at Bedford.—The fifth and 
sixth inquiries involve so many considerations, and require a still so much 
greater number of observations, that no conclusions can at present be drawn 
in reference to them : and in the seventh, the comparison of the Baroscope and 
the use of other instruments, different in principle, but all exhibiting changes 
in the atmospheric pressure, will be employed. 
Among the comparisons which I propose to institute, those with the inva¬ 
luable observations made at different stations, during the late Captain Foster’s 
scientific voyage of discovery in the Chanticleer, by that lamented commander 
and the officers who accompanied him, and which the President and Council 
have, at Mr. Lubrock’s request*, allowed me to make use of for this purpose, 
will be the first and most important; and their value will be enhanced by the 
comparison which, through the permission Captain Beaufort has kindly 
* The interest taken by Mr. Lubbock in my inquiries, the encouragement he has so constantly 
afforded me in the prosecution of them, and the valuable advice which, on the occurrence of every 
anomalous result, he has been always so willing to give me, require my best acknowledgement. 
