326 Reviews— F. G. R. Price's Gault. 



that there is nothing incompatible in the features of the ground with 

 the existence of such barriers, or rather that there is some evidence 

 in each glen, however slight, of water lines at levels higher than the 

 " roads." There are difficulties in the way of the lower " road," 

 No. 4, which extends through Glen Eoy and Glen Spean, that need 

 discussion, but they are not considered more serious than these which 

 attend the other hypothesis. 



This is followed by a discussion on the Till ; on the parallelism of 

 the Roads ; and the general conclusions drawn by the author from 

 the phenomena in Lochaber and the surrounding district. 



IR IE V X IE "W" S. 



I. — The Gault, being the Substance of a Lecture Delivered 

 in the Woodwardian Museum, Cambridge, 1878, and before 

 the Geologists' Association, 1879. By F. G. Hilton Price, 

 F.G.S. (London, Taylor and Francis, 1879.) 



FEW formations have received a larger share of attention of late 

 years than the Gault, and this may be partly due to the exten- 

 sive exploitation of the Cambridgeshire Phosphate-bed, whose 

 organic remains have been so largely derived from its denudation. 



As the Upper Cretaceous geology of England has been much 

 studied by French geologists, and especially by Dr. Barrois, the 

 Gault and its equivalents have naturally come in for close scrutiny, 

 and the French classification differs somewhat from that usually 

 adopted in this country. Much of this misunderstanding arises 

 from our using the lithological term " Gault," originally a Cambridge- 

 shire provincialism, for all the blue and grey marly clays at the base 

 of the Chalk, whilst the similarly situated glauconitic sands and 

 other beds have been called Upper Greensands, Red Chalks, etc. 



For purposes of mapping, and for economic geology, this is by far 

 the best plan, and indeed the only one that could well be adopted, 

 as the tracing of a merely palaeontological line over a large extent 

 of country where there is only an occasional exposure is practically 

 impossible. The surveyor must therefore be guided in the main by 

 the composition of the beds he is mapping ; where all is clay, he 

 may easily class two very different faunas under one denomination, 

 whilst, on the other hand, as the composition changes, he will be apt 

 to give beds more or less contemporaneous very different titles. 



This is exactly what has happened in the case of the Gault in 

 England. Nothing can be clearer, when, by the help of Mr. Price, 

 we have studied the Folkestone section, which for many reasons 

 must be deemed the typical one, that under the general term "Gault " 

 are included two extremely different formations. 



The one known as the Lower Gault consists of black clays, much 

 subdivided by nodule-beds, and is remarkable for the abundance of 

 its Gasteropoda, and grooved Ammonites, of which A. interruptus 

 may be taken as the type. It is the equivalent of the Albien in 

 part, and would seem to be more extensively developed in France 

 than throughout England generally. Not a single Brachiopod is 



