1857.] Report on the Progress of the Magnetic Survey. 57 



It was therefore considerably warmer than the minimum of the val- 

 leys at the foot of the plateau. Besides the minimum does not 

 take place just before sun-rise, but one or one-and-a-half hour 

 earlier. The reason of this phenomenon is that during the night, 

 the coljL air, which is heavier, flows down along the sides of the hills, 

 and accumulates at the bottom of the valleys, whilst at the top of 

 the small plateau itself, the cold air, which is locally formed by the 

 radiation of leaves and grass, is immediately carried away by the 

 winds into the surrounding atmosphere and re-placed by somewhat 

 warmer air. 



During the day-time the temperature at the top of Umerkuntuk 

 is of course much lower than in the valleys below. During my 

 stay there the highest observed temperature was 75 degrees Fahren- 

 heit, exceeding by 5 degrees Fahrenheit the maximum temperature 

 of all the other days. 



There was only one day quite free of clouds during my stay at 

 Umerkuntuk. Generally, soon after 8 o'clock a. m. quantities of 

 cirri dispersed all over the sky, and mitigated the full power of the 

 sun's rays : they only dissolved themselves partially in the evening 

 before sun-set, some portions remaining even during the night. 



Some rain fell on the 29th and 30th of January. It appeared to 

 have extended over a large area, and greatly affected the temper- 

 ature of the air, cooling it down so that the maximum temperature 

 was lowered more than 5 degrees. 



From Jubbulpore up to Umerkuntuk, a strong South- "West or 

 South wind set in very regularly between 9 and 10 a. m., and con- 

 tinued till 5 or 5-30 p. m. The nights were constantly calm. At 

 Umerkuntuk the wind blew from the same direction, but it was 

 quite calm during the rain falls. There was not the least wind on 

 the journey from Paindra to Eewah, where again a South- West wind 

 began. 



Comparing my meteorological observations with those made during 

 the cold season of 1854-55 by my brothers and myself, in the 

 Southern parts of India, the Deccan, Mysore, &c, I find that in 

 Southern India there is, at equal elevations, never so cold a temper- 

 ature as I observed this season in Central India, in the valley of 

 the Nerbudda, &c. 



I 



