Mr Adie on the Sympiesometer. 
last found, and marking the points con'esponding to these deii- 
dties, until the scale is complete. 
By the above scale, the approximate height will be given with- 
out the aid of a table of logarithms, by subtracting the number 
of fathoms indicated by the Sympiesometer at the under station 
from that indicated at the upper station, the difference being 
the number of fathoms which the one station is above the other. 
Previous to laying this instrument before the public, I wished 
to have it submitted to a fair trial, by comparing it with observa- 
tions made in the same ship with the Marine Barometer. For 
this purpose Quintin Leitch, Esq. of Greenock, the proprietor of 
the ship Buckinghamshire, obligingly sent one of the first 
which I had made with this ship on her voyage from the Clyde 
to the East Indies, in the year 1816 ; and the following is the 
report given of the instrument by the late Captain Christiai^, 
the commander, on his return. 
“ I am glad to say that I consider your Barometer a valuable 
instrument at sea, having given it a fair trial on the outward 
passage to India, by keeping a connect register of it, as well as 
of the common Marine Barometer, taken every third hour, 
night and day, during the passage ; and I not only found that 
it was fully as sensible of the changes of the atmosphere as the 
other barometer, but that it had a great advantage over all 
barometers I have ever seen used at sea, namely, tlfat of not 
being in the smallest degree affected by the motion of the 
ship, which will often make the quicksilver in the common 
tube plunge, or rise and fall, in such a degree as to make it 
very difficult to come within at least one or two tenths of an 
inch of the truth, even in the largest ships. On, the passage 
home I also found it very correct in die indication of the winds 
and weather.” 
An opportunity of trying the Sympiesometer in a very different 
climate occurred last year, when the Expedition under Captain 
Ross sailed to the Arctic Regions. Lieutenant Robertson of 
the Isabella kindly undertook the charge of this instrument, and 
regular observations were made every four hours with the Sym- 
piesometer and Marine Barometer, the results of which were 
highly satisfactory. The observations commenced on the 24th of 
April, in North latitude 51° 39', and longitude 1° 7' E, ; and were 
