Qn Mr. Ly ell's "Principles of Geology:' 215 



of bodies for intervals of temperature which do not commence 

 at the freezing point; for MM. Dulong and Petit, in their 

 memoir Ann. de Chim. et Phys. tome vii., from which the 

 quotations are meant to be taken, have not given the expan- 

 sions for such intervals ; but when the true numbers are 

 computed for these intervals from the other results of Dulong 

 and Petit, they differ materially from those given for them 

 in our English quotations. I am, Sir, 



Your very obedient servant, 



Henry Meikle. 



XXXV. Letter from the Rev. W. D. Conybeare, M.A. 

 F.R.S.'F.G.S. %c. on Mr. LyelPs "Principles of Geology." 



To Richard Taylor, Esq. 

 Mr. Editor, 

 T HAVE just received from my bookseller a geological work, 

 -*- which appears to me (while yet 1 am in very many points 

 compelled to hesitate, if not to differ, as to its conclusions) of 

 the first merit and importance; I mean the " Principles of Geo- 

 logy," recently published by one whom I feel happy to be pri- 

 vileged to call my friend, Mr. LyelL The great interest of this 

 treatise seems to me to arise from its necessary tendency to 

 force the current of scientific attention (so far as this subject 

 is concerned) to certain points of theoretical inquiry, for the 

 investigation of which the science has been for some time 

 growing more and more mature, from the gradual accumula- 

 tion of facts by observation and description; though, as I still 

 think, very much still remains to be done in this humbler path 

 of induction, before a foundation of evidence sufficiently am- 

 ple to support securely the superstructure of theoretical system 

 can be considered as fully laid. Insufficient, however, as they 

 may be to lead to anything like final conclusions, the real na- 

 ture and value of our present materials can only be fairly ap- 

 preciated by so classing and arranging them as to show the 

 exact bearing of each upon the points of theoretical inquiry. 

 This labour has certainly been too much neglected of late 

 years, although it is only during this period that observation has 

 been sufficiently extended to enable us even to commence the 

 task with any prospect of utility. Now Mr. Ly ell's work is, 

 above any others that I have seen, calculated to open this field ; 

 but it is evident that it can be cultivated only by free discus- 

 sion. At first the induction must of necessity be often incom- 

 plete, and the application incorrect : mutual, open and candid, 



yet 



