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alternations of wet and dry, but, in contrast to the second and 

 third periods, the wet and dry here partly change places. Thus 

 we find June having a higher percentage than July, and both these 

 months wet, instead of July and August, this last being in the 

 first period comparatively dry. September and October likewise 

 we find both equally wet months, instead of September being a diy 

 and October a wet one, while November is oftener wet than dry. 

 This transference of wet and diy in different seasons — or, as here, 

 in different decades of seasons — is quite in keeping with what has 

 been remarked above, and it is noticeable also how nearly, on the 

 whole, the alternating periods thus brought out accord with those 

 deduced fi-om my own observations, the chief difference seeming to 

 be the rather earlier commencement of both the suramer and 

 autumn rains in Cambridgeshire, where the rainfall is so small, 

 than the same wet periods as estimated by Mr. Gaster's tables, 

 where I have carried the limiting yearly amount up to 35 inches ; 

 and this is just what his law would lead us to expect. This 

 agreement seems to impart a degree of trustworthiness to my own 

 results, and the more so from the circumstance of my having 

 drawn them out before I was aware of the existence of the tables 

 published by Mr. Gaster. 



Perhaps a rationale of these periodical interchanges of wet and 

 dry may be attempted in this way. The spring half of the year is 

 always comparatively dry, with a prevalence of north and north 

 easterly winds. During the three summer months, the ordinary 

 winds are north west, varying occasionally to south west, and the 

 dry weather continues until, after the solstice, the mean daily 

 temperature beginning to decline causes a precipitation, and the 

 first wet period sets in. If the winds continue long in that quarter 

 the rain after a time subsides, and a dry period ensues, reaching 

 more or less into the autumn. Later in this season the north 

 west winds are exchanged for south west, and the rains return from 

 the gi-eater humidity of the latter winds, at the same time that 

 the temperature keeps falling, causing a second wet period. This 

 order of things, however, is of course subject to much interruption. 

 The normal winds for the respective seasons are often out of place, 

 and this causes the variableness of our climate. If the south' 



B 



