168 SCIENCE PROGRESS 



be found with certainty in one of these books or by reference to the indexes of 

 the Zentralblatt or some other abstracting journal for the years subsequent to the 

 date of publication of the dictionaries above mentioned. Coming now to the 

 method adopted in the book, one cannot help feeling that it is the product of the 

 one guiding mind ; which has originated and developed the system, and is 

 thoroughly familiar with its intricacies, but it is somewhat questionable whether 

 other minds will take quite as kindly to it as the author's. It cannot be denied 

 that it is quite a little study in itself to master the system of classification and 

 nomenclature adopted by the author, and any one using the book without having 

 thoroughly familiarised himself with the exact shades of meaning attached to 

 the terms order, genus, division, section, species, specific, semi-specific and 

 co-ordinating tests runs a serious risk of taking the wrong turning and getting 

 lost. It is true that by using the index and looking up the characteristic tests 

 of any particular compound much useful information may be gathered, but this 

 is hardly the way in which the book is meant to be used. The author has no 

 doubt been at great pains to perfect his system, and there is evidence of much 

 conscientious work in the book, but it may be doubted whether the result attained 

 is commensurate with the great labour involved in its production. 



P. H. 



GEOLOGY 



The Rhythmic Deposition of Flint. By Prof. Grenville A. J. Cole, M.R.I.A., 

 F.G.S. {Geological Magazine, N.S., Decade VI, Vol. iv., pp. 64-8, 

 February 1917.) 



" The Rhythmic Deposition of Flint," by Prof. Cole, is a suggestion that Liese- 

 gang's experimental work on stratified precipitation in jelly may be applied to 

 explain the layers of flint nodules in the upper chalk. Liesegang, according to 

 Prof. Cole, " pictures a solution of silica or a silicate spreading through a fairly 

 uniform sediment. Or, in the case of the chalk, the silica may have been at first 

 distributed with approximate uniformity, and then became affected by a pro- 

 gressive ' one-sided ' precipitation." If this explanation of the origin of the layers 

 of flint be accepted, the obvious difficulties on the old view of periodic sponge 

 growths are removed. The crux of the matter seems to be whether the labora- 

 tory experiments on the precipitation of silver bichromate in jelly have any real 

 analogy with anything which could be supposed to happen in the case of silica 

 diffused through calcium carbonate. Could such precipitation occur without 

 some exciting cause, such as the sponge layer might be supposed to supply ? And 

 more especially, does it account for the fact that the flint layers are formed of 

 separate nodules instead of continuous strata as in the laboratory experiments ? 

 Liesegang himself suggests exciting causes or starting-points — " Keime" — for pre- 

 cipitation which may be radiolaria or the hollows of molluscan shells. Which 

 seems to be almost admitting the need of definite lines of some form of organic 



growth. 



G. W. BULMAN. 



The Lower Oolite of North Oxfordshire. By Edwin A. Walford, F.G.S. 

 [Pp. 15, with 7 illustrations.] (Banbury : 71, High Street, 1917.) 



An interesting study of the details of the Lower Oolite as it occurs in North 

 Oxfordshire. Such minute investigations of local geology are of no little import- 

 ance for the general progress of the science. The information, as the writer tells 

 us, has been gathered chiefly from railway cuttings. 





