54 E'ffect of the Pressure of the Atmosphere on the Ocean. 
of observation an interruption in one of the series occurred in eon- 
sequetice of the tide-pole of the “ Enterprise” having been drawn 
up the ice, to the under part of which it had become frozen. 
The amount of displacement of the pole was easily determined 
bya comparison with that of the “Investigator,” but several days 
elapsed before it could be satisfactorily fixed at the same point in 
which it had been originally. The observations of these forty- 
seven days are those which are given in the paper, and their dis- 
cussion is the immediate object of the communication. 
It is stated that subsequent observations seem to show that, 
from the time of the interruption to the middle of July, there 
$a progressive elevation of the mean level of the sea, which 
although of small amount, was sufficiently evident from month 
to month to render the subdivision of the series desirable, in order 
that the individual observations of each separate division should 
be strictly comparable. 
The height of the sea and the corresponding height of the 
mercury 10 ‘the barometer, at every hour in each day, from the Ist 
November to the 18th December 1848 are given in tables. In 
these the arithmetic mean of the hourly heights of the sea for 
each day is taken as the mean level of the sea for that day, and 
the meau of the hourly heights of the barometer is taken as the 
corresponding height of the barometer. These mean levels and 
corresponding mean barometric heights are given in another two- 
column table, arranged in the order of the days of observation ; and 
in a third table these are arranged in the order of the heights of 
the barometer with the corresponding mean agora without regard 
to the dates of observation, for the purpose of showing the de- 
pendence which the latter have on the former 
On these tables the author makes the following remarks. The 
forty-seven days of hourly observations give for the mean height 
of the baromerer 29-874 inches, and of the mark of the mean 
level of the sea 21 feet O-21 in. 
rea pn wan hy { 30227,*and of corresponding level 20 feet 8-4 inch. 
anger ay 
paeeye oaks fe 9559, and of corresponding level 21 feet 5:4 inch. 
Diff +0:668 Diff. — 9-0 
Thus a difference of pressure equal to 0-668 inch produced a 
difference of 9 inches in the mean level of the sea. As the ratio 
of 9 to ‘668 is 13-467 to 1, the author considers that the effect 4 
the pressure of the atmosphere on the level of the sea is 13-467 
times as great as the effect it produces on the mercury in the ba- 
rometer, or very nearly in the inverse ratio of the specific gravities 
of sea-water and mercury. He however states that this remark- 
able coincidence must be considered in a great measnre acciden- 
tal, for if a greater number of days’ observation be taken in order 
