Correspondence — H. A. Baker. 423 



question at issue. The results seemed to me interesting and worthy 

 of print. Yet while being the first to admit the scantiness of my 

 data, I cannot bring myself to agree with a policy which refrains 

 from any kind of cartographical expression until ample data have 

 accumulated. Compaiative treatment and correlation of items of 

 information in ways such as I have adopted, as well as being the 

 strictly scientific method of procedure, is that which puts each item 

 to its maximum of utility. I am convinced that field-geologists 

 would often save themselves much haphazard wandering if they 

 made greater use of cartographical methods beforehand. It is true 

 that very limited data produce very generalized results, but the 

 method works out its own salvation in the long run, and the results 

 then achieved are unattainable in any other way. It is very faint 

 praise to say that " when the amount of evidence available is larger, 

 the method may be of some value ". Had I been in the more 

 fortunate position of Mr. Bromehead, I should long ago have given 

 cartographical expression to my data. The result would have been 

 M map full of imperfections, and doubtless in places at variance with 

 field observations. Yet the steady incorporation of each fresh item 

 of information would bring that map nearer and nearer to perfection 

 and more and more in agreement with field observations. 



Much as I should like to, I am unable, at the moment of writing, 

 to discuss in any detail with Mr. Eromehead the other points which 

 he raises. He remarks that " it seems natural to ascertain as far as 

 possible the zone of the Chalk immediately underlying tlie Tertiary 

 at the boundary of the latter, and to check the zones whose presence 

 beneath. -the Tertiary is deduced from borings by these facts". 

 I take it, then, that if Mr. Bromehead observed the Marsupites zone 

 (say) immediately underlying the Tertiary at the boundary of the 

 latter, he would naturally expect to find the same zone beneath the 

 Tertiary cover. This seems to me a wilful ignoring of the teachings 

 of tectonics, and since we already know that a strong unconformity 

 exists between the Tertiaries and the Chalk, a most unsound view 

 to take. 



With regard to the "series of gentle folds whose axes run about 

 E. 15° S.", referred to by Mr. Bromehead, I spent considerable time in 

 1913 studying these as well as evidences of disturbances of quite 

 different relationship. A fact which made a profound impression 

 upon me was that whereas in the Isle of Wight the Upper Chalk is 

 1,200 feet thick, in Dorset 1,000 feet, in Berks 800 feet, and" in 

 ]^orfolk 1,000 feet, yet in the London Basin, beneath the Tertiary 

 cover, it is often less (and in places considerably less) than 300 feet. 

 In view of this and many other facts, I concluded that while the 

 evidence of a system of approximately east and west folds, including 

 those referred to by Mr. Bromehead, was indisputable, yet this 

 folding did not take the place of premier importance in determining 

 the character of the denudation undergone by successive members of 

 the Mesozoics, including the Chalk. The interesting items of field 

 observation cited by Mr. Bromehead support his tentative suggestion 

 of a set of approximately east and west folds in the Beaconsfield— 

 Winkfield area, and it should be borne in mind that these 



