26 THE BOOK OF NATURE STUDY 



periods the conversation at home and abroad usually deals largely 

 with the weather, and the members of the class will be delighted 

 to offer their contributions, in the shape of the observations that 

 they have made. At the same time the teacher should compare 

 the local fall with that in other parts of the country, comparing 

 the local flooding of the streams, if any, with that in other dis- 

 tricts, until the connection between inches of fall as measured by 

 a rain-gauge and the rain as seen, and as it affects the streams, is 

 clearly grasped. One would at the same time note whether the 

 rain is or is not accompanied by wind, and if so, from what 

 direction the wind is coming. 



In an autumnal rainy period the opportunity would of course 

 also be taken to point out that all the long summer the warm air 

 had been taking up water vapour, and that with the cooling of the 

 air in autumn this vapour descends as rain. As a general rule the 

 rainy winds come up from the Atlantic, and the rain which descends 

 has been gathered as vapour from all that great expanse of water 

 which lies to the west of us. As a contrast one would take a dry 

 period in spring, when the winds are often easterly and cold. They 

 have, as we have seen, been sweeping over a land area before they 

 reached us, and are usually more or less dry as well as cold. 



3. BRITISH RAINFALL. It is no part of our business here to give 

 in detail the conditions in regard to precipitation which exist in the 

 British area, but it may be well here to briefly mention some of 

 the facts to the demonstration of which the school observations 

 should be directed. 



Reference to the literature of the subject (see below) will show 

 that the mean annual rainfall of the whole British area is about 

 38 inches per annum, but, as any rainfall map will show, the state- 

 ment is absolutely useless as affording any guide to the conditions 

 likely to be observed in any given locality. The whole of the west 

 coast of Ireland, and all the elevated parts of the west of Great 

 Britain, have a rainfall considerably exceeding 40 inches, the 

 annual fall rising at places like Ben Nevis to about 160 inches. 

 Again, portions of the eastern seaboard, both of England and 

 Scotland, have a fall below 25 inches, this being especially true 

 of the " wheat belt " in England. From these statements there 



