On Draining. 



47 



pair the completeness of the parallel ; but it must be recollected 

 that whatever corrections are to be applied on these grounds 

 must be in a direction to increase the contrast, and therefore to 

 strengthen the inferences which it suggests. 



We will take Derby, therefore, and place it side by side with 

 Bedford, viewing the latter as the representative of the counties 

 lying around it, and the east of England ; and there can be little 

 doubt that our reasoning might almost with equal truth include 

 the greater part of the southern and central tracts also ; especially 

 when the comparison is to be made, ultimately, not with the 

 climate of DerlDy itself, but of a district like this, differing from 

 it much more than theirs does from that of Bedford. 



The following, then, are the statements to be compared : — 





Elev. 



Mean Temperature. 



Year. 



Summer 





in Feet. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 





Temp. 



Bedford 





o 



38'08 



o 

 41-6 



o 



45-26 



o 



49*89 



o 



58']6 



o 



61*11 



o 



64-31 



o 



62-61 



o 



58*03 



o 



53*46 



o 



45*26 



o 



41*77 



o 



51*64 



o 



62*68 



Derby. 



160 



35-0 



40-5 



40'0 



43-5 



50-5 



53-0 



55-5 



54-5 



51*0 



44.5 



37*5 



33-5 



44*92 



54*33 



Let me now first direct your attention to the mean summer 

 temperature of the two places. At Bedford it is 62° 68' ; at 

 Derby only 54° 33'; showing a difference of no less than 8° 35' 

 in favour of the former ! Consider for a moment the effect of 

 such a continued excess of temperature upon the moisture of the 

 soil ! But it must be farther recollected that this expresses a 

 vieaii alone — first, between the extremes of the whole season, 

 but, secondly, also between those of each night and day ; and that 

 the results of the evaporating poicer would depend more upon the 

 higher extreme, or average greater heat, than upon the daily or 

 monthly mean ; such power being only temporarily checked or 

 suspended, but in no sensible degree reversed or neutralised, 

 by the cold of night alone, when there is no positive accession 

 of moisture during that short interval. Now, this last condition 

 is not only not to be assumed, but there is strong reason for 

 believing it would interfere less in a climate of higher, than 

 in one of lower, temperature. There are two other tables 

 supplied by Mr. Whitley : first, of the fall of rain at various 

 places ; and, secondly, of the mean difference between night and 

 day at six out of this number. If we take from these six, two 

 known to belong to the list of drier climates, namely, Chiswick 

 and Norwich, and two, Truro and Whitehaven, as undoubtedly 

 included among the more humid, we find that, in proportion as 

 the atmosphere exhibits the latter character, the difference be- 



