196 Mr, J. F.. Daniell on the 
will be found that less importance attaches to the omission in this 
particular instance than might at first be supposed. In the last 
voyage, more especially, the precautions which were adopted to 
secure this important. end, were eminently successful. It appears, 
for instance, by Captain Parry’s register, that in the months of 
October and November, the mean temperature of the external air 
varied 32°, while that of the air of the lower deck only 
varied 5°, so that the changes in the course of the 24 hours 
could have been scarcely appreciable. The return of the various 
expeditions which are now about to depart once more for the 
Arctic Regions, the officers of which have most zealously under- 
taken to make the observations with all the requisite precautions, 
will, it is to be hoped, set this interesting question at rest, and not 
only determine the existence of the phenomenon which I have 
ventured to anticipate, but also the exact amount of the fluc- 
tuation. 
I would here willingly have entered into some speculations upon 
the mean height of the barometer as shewn by the registers of 
the high latitudes, and which appear, upon the first view of the 
subject, to be considerably below those of the more southern 
regions, but doubts respecting the construction of the instruments 
destroy the necessary confidence in the observations. These 
doubts are more strongly than ever impressed upon my mind by 
the inspection of eight barometers which were prepared for the 
expedition which has just sailed from the river, by one of the first 
opticians in London, and who undertook to bestow unusual pains 
in their construction. No two of them agreed in height, and the 
greatest difference was full 0.2 of an inch, One standard barome- 
ter, however, now accompanies them, and may serve to determine 
the errors of the others, so that little doubt exists that we shall 
at length be able to arrive at some precise conclusions respecting 
the fluctuations of the atmosphere in the most interesting and 
inaccessible climate of the northern hemisphere. 
The advantages to be derived. from a proper attention to the 
construction of the barometer cannot be better exemplified than by 
the circumstance of the same_ instrument-maker having since 
