CLOUDS SUEMOUNTING FORESTS. 43 



vegetation than in a barren, sterile, stony district, probably by heat 

 being absorbed and retained in a latent form by the process of 

 vegetation in the one case, while in the other it is reflected 

 unchanged. In consequence of this, if a wind in any degree hotter 

 blow over the district covered with trees, this wind is cooled down ; 

 its power of holding water in a state of vapour is thereby diminished, 

 in a geometrical ratio, with every fall of temperature, and a large 

 deposit of moisture may follow in the form of dew, of mist, or of rain. 



The deposit may be much greater than may seem to be pro- 

 portionate to the fall of temperature, but a reference to the 

 observation of Sir John Leslie, and others, that a fall of temperature 

 from 121* to 86®, which is not impossible in a semi-tropical country, 

 occasions a deposit of half of the whole of the moisture held in 

 solution, which is sixteen times as much as could be held in solution 

 by air at 32°, eight times as much as could be held at 53°, and four 

 times as much as could be held at 70°. 



In illustration of what deposit of moisture might take place on 

 such a fall of temperature if the air were nearly saturated, and the 

 quantity of air so saturated great, I may quote the following descrip= 

 tive account of one of those storms which frequently relieve the heat 

 of Bengal, given by Mrs Murray Mitchell, in a volume, entitled 

 " Indian Sketches of Life and Travel," lately published. The 

 oppressiveness of the heat is described as such that one's hands 

 " have a boiled feeling, like a washerwoman's who has been all day 

 manipulating in the tub." Outside, the sun floods everything with 

 one white blaze. " Nature is perfectly still, as if awed ; the leaves 

 hang limp and parched ; the grass crumples up and disappears ; the 

 poor birds hide themselves away in any corner where there is a bit of 

 shade ; there is not even a fly abroad ; all life seems frightened into 

 quiescence, and mankind — at least the native portion — is asleep." At 

 such a moment the storm suddenly descends. It is thus described : — 



" Last week we arranged a nice little garden entertainment for our 

 native friends, and invited some people to meet them. The green 

 was set with numbers of small tables, covered with cakes, and tea, 

 and ices, and flowers. Seats of all sorts and bits of carpet were put 

 down everywhere. Some of our friends had come, and our garden- 

 party promised to be both pretty and pleasant, when, lo ! Mr Don 

 said quietly, ' Look there ! ' and truly enough a cloud like a man's 

 hand had risen in the west, and we knew what would follow. Con- 

 sternation seized us; we all jumped to our feet; each one snatched 

 up something — chair, table, cups, fruit, everything — and rushed pell- 



