180 Mr. J. Brtce on the Recent Progress of the 



stations on the coast near the sea level, ranges from this amount to 

 82 inches ; at heights varying from 150 to 900 feet, the fall varies from 

 115 to 135 inches; at 1,740 feet on the Kundalla Pass, leading from 

 Bombay to Poonab, 142 inches ; and on the highest points, ranging 

 from 6,000 to 8,640 feet, the highest of the West Ghauts, the quantity 

 deposited varies from 82 to 101 inches ; the maximum being always 

 about 4,500 feet. We have already alluded (Art. 10, 14) to the differ- 

 ent conditions under which the air is placed as regards temperature 

 and humidity, when in contact with a mountain slope, from those 

 which prevail within its mass, when we ascend vertically over any 

 space removed from such disturbing influences. The balloon ascents 

 also illustrate this difference. In open situations above the level sur- 

 face of the ground, the law of Professor Phillips, stated in Article 20, 

 is said to hold good for altitudes in India not passing a few hundred 

 feet. 



Great as is the rainfall here recorded, a still more remarkable case 

 remains,- — that, namely, of the Khasia Mountains at the head of the 

 Bay of Bengal, between Assam and Burmah. We learn from Dr. J. 

 D. Hooker that the south fronts of these hills, which attain a maxi- 

 mum elevation of 6,662 feet, with a general level of 4,000 to 5,000, 

 arrest the cloud-bearing current brought up by the Monsoon from the 

 Bay of Bengal, and cause a deposition of the moisture along their cool 

 fronts to the enormous amount of 540 inches, and sometimes 610 inches 

 in the year, — a quantity which, if not evaporated from day to day, 

 absorbed, or run off, would cover the surface to the depth of fifty feet. 

 A portion of the cloud-bearing current, however, passes over these hills, 

 and is caught by the higher ranges of the Bhotan Himalaya, which, 

 while arid and treeless below 6,000 feet, above that level are well 

 watered, and nourish a luxuriant vegetation (see Art. 13.) 



Reserving the remaining portions of Meteorology proper, as Pressure 

 of the Air, Radiation, Meteors, &c., for a second Report, we shall pass 

 on now to the collateral subject of Ten*estrial Magnetism. 



TeebesteiaI/ Magnetism. 



(23.) The various branches of physical science have so close a connec- 

 tion with one another, that it is difficult to adopt a classification of 

 them which-shall be quite satisfactory. To explain the phenomena of 

 one branch, the laws of another must constantly be referred to. This 

 is especially true of Meteorology, whose multiplied objects and many 

 complex problems ally it to geography, astronomy, chemistry, optics, 

 and pure physics, and require the aid of the higher mathematical ana- 

 lysis. As referring to the great physical agencies at work in the earth's 



