1851.] On the Comparative action of Aneroid Barometers, 221 



1 have found then with great satisfaction an instance in which the 

 Aneroid, Mercurial Barometer and Simpiesometer have been carefully 

 registered in a Cyclone, though not one of the very severest class, and 

 moreover one in which the fall of the Barometer was trifling as 

 compared with many of which we have full details. Nevertheless as 

 the first instance of the kind on record, and with the hope of leading 

 public attention to this very important scientific question — for the 

 great portability and convenience of the Aneroid are very tempting 

 advantages to induce many seamen who can ill afford money or room 

 for a multiplicity of instruments, to substitute it wholly for the Baro- 

 meter and Simpiesometer, — I have thought it useful that the details 

 should be published. 



This instance has been furnished to me by Mr. Branch Pilot S. 

 Ransom of the H. C. Pilot Brig Tavoy, which he commanded in the 

 April Cyclone of 1850, and it will be sufficient to state here that the 

 Cyclone was one which has been traced from near the Nicobar Islands 

 to Moorshedabad, a distance of 1,000 miles. 



Its centre passed at about 2 a. m. of the 27th April about 60 miles 

 to the West of the Tavoy, which vessel was then cruising at the Pilot 

 Station and had put to sea to get an offing. Mr. Ransom has given 

 a very full series of observations of which the result for 36 hours will be 

 seen by the following tables to which I have interpolated the differences : 

 the principal results being given first, to save room, and Mr. Ransom's 

 detailed table last. 



The principal results are as follow. 



26th April, 1850, Mar : Bar. Biff. Aneroid. Biff. Simp. Biff. 



At 2 a. m. 29.77 29.94 30.05 



— 0.14 — 0.16 — 0.35 



2 p. m. 29.63 29.78 29.70 



— 0.26 — 0.25 — 0.25 

 27th April, 2 a. m. 29.37 29.53 29.45 



+ 0.33 + 0.32 -f 0.34 



2 p. m. 29.70 29.85 29.79 



2 f 2 



