20 Meteorological Observations on Parisnath Hill. [No. 1. 



occurrence may at least be admitted. Such an admission will be 

 sufficient to encourage further investigation into the subject. 



An explanation of such a phenomenon would not only require a 

 favourable state of the atmosphere, and observations extending over 

 a greater number of days, but also accurate determinations of mois- 

 ture and the direct observation of the greater or smaller resistance 

 which the atmosphere offers to the passage of the sun's heating rays. 

 It would besides have to take into account the changes in the speci- 

 fic gravity of the air with a rising and falling Barometer- 

 Particular care would have to be taken to guard the thermometers 

 against the influence of direct radiated and reflected heat from the 

 ground. No other climate is so well adapted as that of India to 

 bring to a satisfactory conclusion an examination into the conditions 

 of such a phenomenon, and stations in similar relative situations as 

 Parisnath hill and Calcutta may be found in many parts of the 

 country. 



The course of the hourly mean temperatures of the stratum 

 of air presents another difference from the means of the stations. 

 In India the minimum temperature is, as a general rule, observed 

 at 6 a. M., this being the first hour of observation after, or the 

 last hour before sunrise. In the present iustance the minima 

 in the curves of the stations, for both days, fall upon 6 a. m. It 

 is different with the curves of real mean temperatures of the 

 stratum of air. On the 1st, we find the minimum at 7, — on the 2ud 

 and 3rd the hours of 6 and 7 had not been observed, — but on the 

 4th the temperature at 7 has not risen above that at 6. It is 

 not surprising that the lowest temperature of the air, far re- 

 moved from the ground, should occur a short time after sunrise. 

 The air receives its temperature chiefly from the ground and some 

 time must be required to heat the latter, and also to communicate 

 this heat to the air in which, in the mean time the process of cool- 

 ing must go on. I have (at Baroda), only six feet from the ground, 

 in the shade of a house towards the North and protected from the 

 rays of the rising sun, frequently observed the temperature still 

 falling for a quarter and half an hour after sunrise, the decrease 

 between sunrise and the moment when the temperature commenced 

 to rise again amounting to 2 or 3 tenths of a degree Centigrade. 



