214 Notices respecting New Books. \, 



however to lessen its influence; and it does not therefore 

 altogether supersede the eflfects of that changeableness, 

 which consists in a great extent of variation of the tem- 

 perature of two successive days, or of different hours in the 

 course of the same day. The simplest, and perhaps the 

 best mode of appreciating the effect of the extent of such a 

 variation, in deteriorating a climate, is to observe, for each 

 month, the greatest variation, at the same hour, in any two 

 successive days within its duration. The mean variation 

 of successive days may also be computed, in order to assist 

 in the comparison ; and the mean diurnal range, or the 

 space through which the surface of the mercury moves, in 

 ascending and descending, throughout the day and night, 

 will give a collateral estimate of a similar nature. The best 

 practical mode of deducing this range from the observations 

 is, to find separately the mean of the heights for the morn- 

 ing and afternoon, and to double their difference. Where 

 none of these particulars can be obtained, the extreme va- 

 riation of each month will afford a character not altogether 

 unimportant. 



[To be continued.] 



XXXIV. Notices respecting New Books. 



Mr. Farey's Mineral and Agricidtztral " Report on Der- 

 byshire." 



JL HE first chapter and volume of this work have been some 

 time before the public: in our xxxixih volume, pages 192 

 and 253, v.e gave extracts from this volume, and made re- 

 ferences to three previous communications from Mr. F. 

 inserted in previous volumes, of matters contained therein, 

 though under different forms of arrangement. We have now 

 10 notice aif'co/jcfvolumeof this important work, containing 

 chapters 2 to 13, treating of the subject usually embraced 

 "by the County Reports of the Board of Agriculture j but 

 treated most of them, as appears to us, with a degree of 

 precision in all matters relating to persons, improvements, 

 places, soil,, strata, &c. which has not, we believe, been 

 attempted in any of tlie other reports, though their utility 

 depends so much on such particulars. 



In the chapttr on woods and plantations, we find the 

 subject oi pruning and training up young plantations ably 

 treated, and at considerable length, as one which previous 

 reporters had rather surprisingly overlooked, and the sug- 

 gestions of the author seem to us calculated to obviate, ia 



time, 



