1837.] 



Meteorological Observations at Moulmein. 



47 



III — Abstract of Fight Months' Meteorological Observations at Moul- 

 mein.— 'By James Dalmahoy, Esq. of the Madras Medical Estabiish- 

 ment. Physician to His Highness the Rajah of Travancore. 



The accompanying tables furnish a few data respecting the periodi- 

 cal oscillations of the barometer, and the heating power of the sun's 

 rays at a station wilhin the tropics. They contain also some other obser- 

 vations usually supposed to be connected with the movements of the 

 barometer. As they refer to a period of eight months only, no general 

 conclusions regarding the climate can be deduced from them, and there- 

 fore it was thought unnecessary to give a mean at the foot of each 

 column. 



Moulmein or Maulamyne, the principal station in the Tenasserim 

 provinces, is situated in 10° 30' N. L. and I believe about 97° 30 < E. L. 

 It may be considered at the level of the sea, for the river, on the bank 

 of which it lies, has free communication with the sea not eight miles to 

 the westward, besides its more distant mouth at Amherst to the south. 

 The observations were made at the height of thirty or forty feet above 

 the surface of the river. 



The barometer employed was a portable one of the syphon kind, and 

 therefore required no correction except the reduction of the observa- 

 tions to a common temperature. The sound produced by striking the 

 mercury against the top of the tube indicated that there was no air in- 

 terposed. In making the observations, precautions were used to obviate 

 the effects of friction between the lube and mercury. The barometer, 

 also the wet-bulb thermometer, and one exactly similar for ascertain- 

 ing the temperature of the air, were made by Mr. Robinson, of London, 

 The thermometers were graduated to quarters of a degree of Fahren- 

 heit's scale. The maximum and minimum thermometers were made 

 by Mr. Adie, of Edinburgh, whose plan of introducing naphtha, above 

 the mercury, in the former instrument, is completely successful in 

 preventing the retraction of the index. The actinometer,* an instru- 

 ment invented by Sir J. Herschel, was made by Mr. Robinson. It was 

 observed only at apparent noon, and the glass plate in front of the bulb 

 was always placed at right angles to the direction of the sun's rays. 

 In making an observation, a board, just sufficient to intercept the 

 direct rays of the sun, was held at some distance by an assistant, and 

 the rise of the instrument during one minute was noted ; the board was 

 then suddenly withdrawn, and the rise during an equal interval again 

 noted ; the rays being once more intercepted, an observation similar 



* See Reports of the British Association, &o. vol. ii. p. 379. 



