Intertropical Springs and Bivers. 



109 



sheltered by a thatched roof. Every precaution enjoined by M. 

 Boussingault was carefully attended to, and fresh holes bored every 

 day. 



Experiment. — First Day. 



Sunrise, 

 2 p. M., 



Sunrise, 

 2 P. M., 



Sunrise, 

 2 p. M., 



Sunrise, 



2 P. M., 



At Cassergode, on the west coast, lat. N. 12°- 29, whose mean 

 temperature is about 80°, the diurnal fluctuation amounted to only 

 l°-5 in cloudy weather. At Mangalore, on the same coast, lat. 

 N. 12°.53, it amounted, on a clear day, to 2°*75. The last expe- 

 riment was made at my request, by my friend Mr B. G. Maurice, 

 Madras Medical Service. In stiff clayey soils, at the depth of four 

 feet from the surface, and sheltered to the distance of six yards, 

 radius from the spot perforated, the temperature fluctuated but 

 little, and gave a tolerably correct m«an of the air. In light 

 sandy soils a greater depth is necessary, and at all times it is advis- 

 able to observe the temperature of the perforation in the soil at the 

 coldest and hottest periods of the day, which, with an unclouded sky, 

 will be found to occur at, or just before, sunrise, and from 2 to 3 

 p. M. Such observations should, if possible, be compared with the 

 temperature of a spring or well of moderate depth, at from six to 

 ten feet below the surface, bearing in mind what has already been 

 stated regarding the causes affecting the temperature of wells and 

 springs. — Philosophical Transactions of Royal Society of London, 

 1845. Part L p. 155. 



