1810.] the Action of Nitric Acid on Lithic Acid. 365 



iig human calculi, . even when purified as well as possible in the 

 nlanner commonly recommended. I always used m my ex- 

 periments pure lithic acid, prepared from the excrements of the 

 serpent exhibited as the boa constrictor, from which purpuric 

 acid may be readily obtained by the method pointed out in my 

 paper. 



'to bi 



Article IX. 



Analyses of Books. 



A Critical Examination of the first Principles of Geology ; in a 

 Series of Essays. By G. B. Greenough, President of the 

 Geological Society, F.H.S. F.L.S. London. 



{Continued from p. 3C9.) 



II. On the Figure of the Earth. 



Tins essay contains a very learned and elaborate discussion 

 respecting the cause of the inequalities which at present exist 

 upon the surface of the earth — a subject which has been very 

 much discussed by geologists, and respecting which a great 

 variety of opinions have been advanced. If we were disposed 

 to look out for faults in this elaborate essay, which exhibits 

 much learning and much practical knowledge of the structure of 

 the crust of the globe, we would remark, that it is rather defi- 

 cient in that precise arrangement, that lucidus ordo upon which 

 a very great portion of the value of scientific writings depends. 

 The reader, before he can appreciate the value, or even under- 

 stand the full amount of the information communicated, must 

 be nearly as well acquainted with the subject as the author him- 

 self ; yet surely it is not for those who are already proficients in 

 geological investigations that these essays are intended ; but for 

 those who have not yet made up their minds respecting the great 

 points under discussion, and have not yet enlisted themselves 

 under the banners of any leader. In a science abounding, like 

 geology, in many vague and conjectural speculations, concerning 

 which, absolute certainty being out of the question, we must 

 rest satisfied with ingenious reasonings, or plausible conjectures, 



-itlis ; not likely that any essay,, however learned or accurate it 

 may be, will be capable of shaking the faith of any staunch sup- 



-JipiGrter of a favourite creed. No Werneriau will give up his 

 formations, his chemical and mechanical deposits, his alternate 

 / r.t reals and rclnrns of, the original ocean in which all things were 

 di^ttlved, nor, the gradual diminution of the level of the d$%$nt 

 rocks according' to the order of their deposition. The faith of 

 no Y'.lc.miKf will br- shaken in the volcanic nature of basalt, 

 greenstone, and porphyry-slate, and in the identity of these r<5, C k« 



