44 
PROCEEDINGS OE SOCIETIES. 
MONDAY, DECEMBER 14, 1857. 
James Henthorn Todd, D. D., President, in the Chair. 
The Rev. Robert Carmichael read a Paper on the Singular Solu¬ 
tions of Partial Differential Equations. 
William Kelly, M. D., R. N., read the following Paper on— 
THE ANNUAL VARIATIONS OF ATMOSPHERIC PRESSURE IN THE GULF OF 
ST. LAWRENCE. 
The Table which accompanies this Paper is an abstract from the 
“Meteorological Journal of the Naval Surveying Party” on the St. 
Lawrence. The observations from which it is taken extend over nine 
years, from 1841 to 1850. They were made on board the Gulnare 
surveying vessel, from the end of May in each year, to the middle of 
October; and during the remainder of the year at Charlotte Town, 
Prince Edward Island, where the party wintered. 
Two ordinary marine barometers were employed in making these ob¬ 
servations. The first got out of order in June, 1845, and the second was 
not obtained until the September following. The indications of the 
latter were somewhat lower than those of the first, which agreed gene¬ 
rally with other barometers of the same construction. There was no 
apparent difference, however, in the range of the instruments, which, it 
is scarcely necessary to say, was less than the true range; not only on 
account of the varying level of the mercury in the bag, according as it 
ascends or descends in the tube; but also from hygrometric causes act¬ 
ing on the bag itself; the instruments having been kept in the moist air 
of a vessel at sea during the summer, and in the dry air of a house 
warmed by stoves during the winter. 
* Erom the mean of all the observations we find that the atmospheric 
pressure is least in January, February, and March; that it increases 
slowly in April and May, and that there is a very slight decrease (*01) in 
June; that the pressure is greatest in July, August, and September, 
after which it decreases gradually through the three remaining months 
of the year. 
The annual course of atmospheric pressure which we find here, on the 
north-east coast of America, derives interest from the fact that a similar 
course has been as yet observed only at Sitka, on the extreme north-west 
of the continent, and in Europe at considerable mountain elevations. 
Nothing apparently connected with it, either by similarity or contrast, 
has been observed on the mainland of North America; but in the sea to 
the north of the continent, which in following the coast-line may be 
said to lie between Norfolk Sound and the Gulf of St. Lawrence, we find 
an annual course of atmospheric pressure, decidedly different from that 
which obtains in these seas. 
