68 Br. Aubrey Strahan — Geology at the Scat of War. 



may start the segregation is hardly sustained hy the examples that he 

 brings forward. The "tests of sea-urchins and bivalve shells" are 

 not very often "converted into flint". Casts of their interiors are 

 common enough, and flint often encloses the calcareous tests. The 

 infilling of calcareous ooze has become silicified, like the chalk 

 surrounding the remains. The test, especially when formed of 

 calcite, has resisted pseudomorphism. 



There is something inspiring in the conception of a thousand feet 

 of chalk, with an area of some thousands of square miles, acting as 

 a medium for waters which rearrange the silica left by organisms 

 throughout its mass. It remains to be seen if field-observations raise 

 any serious objections to this view. If we could find limestones 

 contorted at so early a stage that the zonal silicification set in at a 

 later date, the zones of flint should be independent of the planes of 

 stratification. 1 But flints seem, as I have previously remarked, to 

 belong to the first stages of consolidation, when the waters are being 

 drawn up or sink down vertically through the mass. These waters 

 group the silica as they diffuse, and they emerge or drain off elsewhere 

 in the form of calcareous springs. 



Though flint in other limestones is often spoken of as chert, our 

 considerations must be by no means limited to the siliceous nodules in 

 the Chalk. Reversing the opinions that we formerly held, we may 

 see in the rhythmic deposition of flint an indication that the silica 

 was originally evenly distributed in the mass. When layers of varying 

 texture and mineral composition are present, they check continuous 

 diffusion. The more uniform conditions in the chalk of Upper- 

 Cretaceous age have no doubt given us a classic example ; but nodular 

 layers, and even regularly surfaced beds of flint, are known to most 

 workers in the Carboniferous Limestone. A fine instance occurs in 

 the steeply dipping strata in a quarry at Ballintemple, east of the 

 city of Cork. The Portland Beds of the south of England, and the 

 white Cainozoic limestones of the Paris Basin, also furnish examples 

 in easily accessible lands. 



IV. — Gkolorv at the Seat of War.- 

 By Aubrey Strahan, Sc.D. (Camb.), Hon. LL.D. Toronto, F.B.S., V.P.G.S. 



AT a time when the resources of every branch of science are being 

 devoted to the furtherance of the War, it is not inappropriate 

 to consider in what way geological research is being turned to account. 

 At first sight it might appear that the work of the stratigraphies! 

 geologist, the palaeontologist, or the petrographer might be of domestic 

 and academic interest, but would be unlikely to influence the course 

 of a worldwide war. Such researches have received a respectful 



1 The only reference with which I am acquainted as to the relation of flint- 

 zones to earth-movement is the remark by W. Hudleston in the discussion on 

 Wallich's paper that flints are absent from ' flat ' beds of Coral Eag at North 

 Grimston, but are present where the beds are bent (Quart. Journ. Geol. Soc. 

 London, vol. xxxvi, p. 92). This interesting observation deserves, and may 

 have received, further investigation. 



2 Presidential Address to the Vesey Club, December 12, 1916 (Abstract). 



