ATMOSPHERE ON THE MEAN LEVEL OF THE OCEAN. 
287 
The ships were not finally placed in their winter position until the middle of 
October, when the operation of fixing the tide-pole engaged our first attention. 
A hole, 2 feet square, was cut through the icy platform, a strong pole, nearly 
40 feet long, passed through it, and driven firmly down several feet into the clay, and 
fixed by heavy iron weights, which also rested on the clay and prevented any move- 
ment of the pole. It was placed in about 21 feet depth of water at the time of mean 
level of the sea, and by the end of the month was considered, and afterwards proved 
to have been so perfectly immoveable, that we began the regular series of observations 
on the 1st of November. 
Another tide-pole was in like manner fixed through a hole in the ice close to the 
Investigator, for the sake of reference and comparison. Hourly observations of the 
tide and the barometer were made by the officers and petty officers of that ship, exactly 
corresponding with those made by the officers of the Enterprize, throughout the whole 
of the nine following months, to the end of July, and they proved of great value in 
many instances, where very large and apparently unaccountable irregularities of the 
tides occurred, and which otherwise might have been attributed to inaccuracy of 
observation, or of registry, or of the shifting of the tide-pole, had they not also been 
observed in every case, at exactly the same time and precisely to the same amount 
at both the tide-poles. 
The reduction of the double series of observations, however, would have so greatly 
increased the labour of preparing this paper as well as its length, that the Investi- 
gator’s observations have, for the present, been only used for comparison in several 
cases of uncertainty above alluded to, and for the purpose of refixing the tide-pole of 
the Enterprize when it was lifted by the ice on the 18th of December. But the whole 
of the observations of both the ships are preserved in the proper office at the Admi- 
ralty, and may at any time be referred to for any purposes of further investigation. 
The hourly observations which were commenced on the 1st of November, were 
continued uninterruptedly until the morning of the 18th of December, when the tide- 
pole having been frozen to the underpart of the ice was drawn out of the ground as 
the tide rose, and thus made the first break in the series, after forty-seven complete 
days. The amount of displacement of the pole was easily determined by comparison 
with that of the Investigator, but several days elapsed before it could be satisfac- 
torily fixed at the same point in which it originally stood. 
Subsequent observations serve to show that from this time to the middle of July 
there was a progressive elevation of the mean level of the ocean, and, although of 
small amount, the difference from month to month was sufficiently evident to render 
subdivisions of the series desirable, in order that the individual observations of each 
separate division should be strictly comparable with the others ; so that this early 
interruption is the less to be regretted. 
The method of observation was as follows : — At the exact hour of mean time the 
heights of the tide and of the mercury in the barometer were taken ; the former by 
the quarter-master, and the latter by the officer of the watch, who immediately entered 
both the observations in the meteorological journal, from which the following tables 
were constructed. 
