264 



THE GEOLOGIST. 



treated with great conciseness, is stamped by broad philosophical views, founded 

 mainly on the teaching of Edward Forbes, " gathered either from his works or troni 

 conversations with liim on the subject." On the classification of the sedimen- 

 tary strata, Mr. Jukes' arrangement differs in some details from that generally 

 adopted. For instance, he classes the rocks usually called the Upper Old Red 

 Sandstone in Scotland, the Upper Devonian in Devonshire (the Marwood, Pilton, 

 and Petherwln beds), and the Upper or Old Red Sandstone proper of the south of 

 Ireland and South AYale?, as Carboniferous strata, placing them at the base of that 

 system. 



Dr. W. K. Sullivan, Professor of Chemistry at the Irish Museum of Industry, 

 has greatly aided Mr. Jukes in the chemical description of the rock-forming 

 mmerals. Many of Dr. Sullivan's observations — which are incorporated with the 

 text — are excellent, and give the clearest views on the subject. There is, how- 

 ever, one point which we think should be pointed out and set right, for if un- 

 noticed, it may place the Doctor in a false position with foreign savants. In his 

 preface Mr. Jukes thus writes : " Dr. Sullivan also examined these descriptions 

 for me, and pointed out a certain relation which might be traced in them, between 

 the proportions of oxygen in the acid and that in the base, by means of which 

 relation the close connection between allied mmerals is made more obvious, and 

 placed on a more systematic basis than hitherto. It vfill be, I believe, of interest 

 and importance to the chemical mineralogist." Now, persons unacquainted with 

 inquiries in this branch of geology might, from this statement, be led to suppose 

 that the relation referred to — which is of the highest importance — was first 

 noticed and investigated by Dr. Sullivan. This is not the case; and we are as- 

 sured the Doctor w^ould not wish such an impression to be conveyed. For some 

 years this relation has been made the basis of classification for minerals and rocks 

 by many continental geologists. A great part of Bischof's reasoning is entirely 

 founded on this relation, which he certainly states in a difterent form, and calls the 

 oxygen-quotient ; but that it is essentially the same will be evident by the follow- 

 ing reference. After pointing out the little vakie to be attached to the ordinary 

 formulas by Avhich the chemical composition of minerals is represented, he pro- 

 ceeds : " The ratio of the oxygen of the silica, and that of the whole of the base, 

 is, on the contrary, independent both of the portion of the bases as monoxides or 

 sesquioxides, and of the orders to which the several silicites belong." — (Transla- 

 tion Cavendish Society, vol. ii., p. 88.) 



In general arrangement this ilfanwaZ is founded on thatof ISTaumami's "Geognosie." 

 Mr. Jukes' division of lithology answers to Naumann's Petrographic, and his 

 petrology to the latter's GeoteUonik ; they have the division paleontology in 

 common. Mr. Jukes' thii-d part answers to Naumann's second volume ; and in 

 the excellent arrangement of the characteristic fossils of each formation, in the 

 mode of marking those that were introduced or became extinct, he also foUows 

 the German geologist. 



On the theoretical principles of geology, the author is an earnest disciple of the 

 views of Sir Charles Lyell, which he propomids with a greater distinctness, perhaps, 

 than they have hitherto been set forth. The whole question of the metamorpliism 

 of sedimentary mto crystalline rocks, and the doctrine of the hypogene derivative 

 origin of granite, are fuUy and clearly stated. 



From what we have said, although portions are more adapted to the service of 

 authors than of students, we need scarcely add we recommend this work to our 

 readers. 



