261 
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 from 
conversations witli him 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 Devonshu-e (the Marwood, Pilton, 
and Pctheru'in beds), and the Upper or Old Red Sandstone proper of the south of 
Ireland and South Wales, 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 
minerals. 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 savanls. In liis 
preface Mr. Jukes thus writes : " Dr. Sullivan also examined tliese descriptions 
for me, and pointed out a certain relation which might be traced in them, between 
the proportions of o.xygen in the acid and that in the base, by means of which 
relation tlic close connection between allied minerals is made more obvious, and 
placed on a more systematic basis than hitherto. It will 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 would 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 different form, and calls the 
oxygm-quotimt ; but that it is essentially the same will be evident by the follow- 
ing reference. After pointing out the little value to be attached to the ordinary 
formulas by which the chemical composition of minerals is represented, he pro- 
ceeds : " The ratio of the oxygen of the sUica, and tliat of the whole of the base, 
is, on the contrary, independent both of the portion of the bases as monoxides or 
sesquioxidcs, and of the orders to which the several silicites belong." — (Transla- 
tion Cavendish Society, vol. ii., p. 88.) 
In general arraiigementthisil/anwa^ is founded on thatof Naumann's "Gcognosie." 
Mr. Jukes' division of lithology answers to Naumann's PetrograjMe, and liis 
petrology to the latter's Geoiektonik ; they have the division paleontology in 
common. Mr. Jukes' third 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 follows 
the German geologist. 
On the theoretical principles of geology, the author is an earnest disciple of the 
views of Sir Charles Lyell, which he propounds with a greater distinctness, perhaj)s, 
than they have hitherto been set forth. The whole question of the metamorphism 
of sedimentary into crystalline rocks, and the doctrine of the hypogene derivative 
origin of granite, are fully and clearly stated. 
From \\ hat we have said, altliough portions are more adapted to the service of 
authors than of students, we need scarcely add we recommend this work to our 
readers. 
