1858.] Meteorological Observations on Parisnath Kill. 



21 



This phenomenon will most likely be observed only under favorable 

 circumstances and in places where the ground remains in the shade 

 for some time after sunrise. Mr. Eadanath Sikhdar in charge of 

 the observatory at Calcutta, where once or twice every month read- 

 ings of the thermometer are taken from ten to ten minutes before 

 and after sunrise,* has noticed the same circumstance. His kindness 

 has enabled me to give the following table, containing the observa- 

 tions made on the 22ud January, 7th and 23rd February and 21st 

 March, 1857. The state of the weather on those days was particu- 

 larly favourable, there having been no clouds or rain, which, in all 

 other months are apt to interfere with the regularity of the pheno- 

 menon. I give the readings in degrees Fahrenheit, the scale by 

 which they have been observed. 



1857. 



Minutes before 



sunrise. 



20 10 



Sunrise. 

 



10 



Minutes after sunrise. 



20 30 40 50 60 



22d January, 



54.0 



53.9 



53.8 



53.7 



53.6 



53.6 



53.6 



53.7 





7th February, 



63.0 



62.9 



62.8 



62.6 



62.4 



62.2 



-62.0 



62.0 



62.3 



23d February, 



70.0 



70.0 



69.8 



69.8 



69.5 



69.4 



69.3 



69.5 



69.8 



21st March, 



74.8 



74.6 



74.7 



74.7 



74.6 



74.6 



74.8 



75.2 





Means, 



65.45 



65.35 



65.27 



65.20 



65.02 



64.95 



64.92 



65.20 





Looking at the means, we find that the lowest temperature took 

 place forty minutes after sunrise and the difference between the tem- 

 perature at sunrise and the lowest temperature, is 0°.35 F. or 

 about 0°.2 C. 



Correction of the Barometrical readings. — The alterations to which 

 it has been necessary to subject the curve of the real mean tempera- 

 tures, in order to reduce its smaller irregular deviations, involve an ex- 

 amination of the barometrical readings from which these temperatures 

 have been derived. From the formula for the calculation of the real 

 mean temperatures, given above, it is seen that the value of theteiu- 

 * Since January 1857. 



