THE SYMPIESOMETER. 



489 



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 pu- 

 blic, I wished to have it submitted to a fair trial, 

 by comparing it with observations made in the same 

 ship with the Marine Barometer. For this pur- 

 pose Quintin Leitch, Esq. of Greenock, the proprie- 

 tor 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 Christian, the 

 commander, on his return. 



f I am glad to say that I consider your Barome- 

 ter a valuable instrument at sea, having given it a 

 fair trial on the outward passage to India, by keep- 

 ing a correct register of it, as well as of the common 

 Marine Barometer, taken every third hour, night 

 and day, during the passage ; and 1 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, that of not being in the 

 smallest degree affected by the motion of the ship, 

 which will often make the quicksilver in the com- 

 mon 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 



