222 Royal Society, 



places, are pointed out, and numerous instances are given of the 

 very great power of the slanting rays of the sun beyond the tropic. 

 As is the case with the barometric, so do the heat tables indicate 

 that the annual and daily ranges of the thermometer diminish with 

 the elevation of the place of observation above the sea-level, the 

 elevated table-land of the Deccan however being an exception to 

 this rule. At Mahabuleshwur, at 4500 feet, the temperature of the 

 air was never below 45° with a maximum and minimum thermo- 

 meter; and at Dodabetta the temperature of the air was never below 

 38°'5, nevertheless at both places ice and hoar-frost were frequently 

 found on the ground at sunrise, resulting from the separate or con- 

 joined effects of radiation and evaporation. 



After stating the want of confidence he has in observations of the 

 wet-bulb thermometer as a means of determining the dew-point, 

 and that he greatly prefers Daniell's hygrometer for this purpose, 

 the author observes that he will not venture to say more with re- 

 spect to normal conditions of moisture in India than that the air of 

 the sea coast has always a much greater fraction of saturation than 

 the lands of the interior ; and that the elevated plateau of the Dec- 

 can is periodically subject to very high degrees of dryness. 



Some very unexpected phenomena with reference to the distri- 

 bution of rain are pointed out. It is found both on the sea coasts 

 and on the table-lands of the Deccan, that within very limited areas, 

 the differences in the fall of rain may be very great. With nine 

 rain-gauges employed in the small island of Bombay in the months 

 of June and July, in the monsoon of 1849, the quantity collected 

 in the different gauges ranged in July from 46 inches to 102 inches, 

 and in June from 19 inches to 46 inches. At Sattarah, in the 

 Deccan, with three rain-gauges within the distance of a mile, they 

 differed in their contents several inches from each other; and at 

 Mahabuleshwur and Paunchgunny, nearly on the same level, the 

 latter place being only eleven miles to the eastward of the former, 

 the annual fall of rain was 254 inches and 50 inches respectively ! 

 The normal conditions are, that there is a much greater fall of rain 

 on the sea coasts than on the table-lands of the Deccan, but that the 

 Ghats intervening between the coasts and the table-lands have three 

 times the amount of the fall on the coasts, and from ten to fifteen 

 times the amount of the fall on the table-lands of the interior ; the 

 paucity of the fall of rain at Cape Comorin and in the mouths of the 

 Indus would also appear to be normal conditions. 



The tables must be referred to for the winds ; the normal states are 

 those of the south-west and north-east monsoons, and the influence of 

 the latter is periodically felt at the height of 8640 feet at Dodabetta, 

 which height would appear just at the upper surface of the stratum of 

 air constituting the south-west monsoon ; but hourly observations for 

 lengthened periods are necessary at Dodabetta, to determine what 

 really are the periodical winds at that height. From the points other 

 than those between south and west, and north and east, there is also 

 at the several stations a certain amount of periodicity in the winds, 

 the winds that are common to different stations having only a slant 



