638 



SCIENTIFIC RECREATTOXS. 



only a wet and dry season, while north and south of the calm region we find 

 rainless districts, or zones tempered by the trade winds, which are dry winds. 



But if we suppose as indeed is the case in South America that these 

 dry winds happen to come in contact with a cool mountain, the moisture of 

 the air is precipitated in rain. In Australia, on the contrary, we have 

 portions of land actually burnt up for want of rain, because the mountain chain 

 breaks the clouds, so to speak, on a limited corner of the island, while the 

 interior is parched. The winds also coming over India from the Bay of 

 Bengal discharge clouds and rain in the Plimalayan slopes. So we perceive 

 that the situation of mountain chains have much to do with the rain-fall, 

 and of necessity, therefore, with the vegetation and fertility of the land. 

 This is another noticeable link in the great chain of Nature. 



Perhaps it may now be understood why westerly and south-westerly 

 winds bring rain upon our islands, and why the counties such as Westmore- 



(I 



Fig. 720. Meteorological Observatory, Pic du Midi. 



land and Cumberland and those in Wales receive, more rain than any other 

 part of the United Kingdom. Seathwaite, so well known to tourists in the 

 lake district, has the proud position of the wettest place in these islands. 

 We find that when the westerly wind sets in it has come across the warm 

 Atlantic water and become laden with moisture, which, when chilled by the 

 mountains, is precipitated as rain. 



The amount of rain that falls in the United Kingdom is carefully 

 measured by rain-gauges, some of which are extremely simple. The water 

 is caught in a funnel-mouthed tube, and measured in a measuring glass every 

 four-and-twenty hours. Thereby we can tell the annual rainfall in any given 

 district, whether it be twenty inches or a hundred. One inch of rain actually 

 means one hundred tons of water falling upon one acre of land. Therefore, 

 if -the annual report of rainfall (including all moisture) be twenty inches, we 

 have an aggregate of 2,000 tons of water upon every acre of surface within 



