178 TRANSACTIONS OF SECTION C. 



mineral composition of the rock as revealed 'by the microscope, is, in fact, at 

 present the most practical method of determining the composition of the minerals. 

 I need scarcely say that volatile constituents still retained by the rock should 

 be separately determined, and the amount reported as water should not include 

 any other substance given off at the same time. 



In the absence of facilities for obtaining rock analyses, petrological work in 

 this country is at present seriously handicapped. A striking illustration of the 

 inadequate provision for analyses is revealed in the fact that for the whole of the 

 early Permian granitic intrusions in the south-west of England, covering nearly 

 2,000 square miles, and including numerous different types and varieties, there 

 are only four analyses in existence, and of these two are out of date and imper- 

 fect. This is all the more remarkable in view of the fact that these rocks are 

 closely connected with the pneumatolytic action that has given us almost all the 

 economic minerals of the south-west of England, comprising ores of tin, 

 tungsten, copper, lead, and uranium, as well as kaolin. If the Survey, by 

 increasing its staff of analysts, were in a position, not merely to multiply the 

 number of analyses illustrating its own work, but to help others engaged in 

 research, they would only be proceeding on lines which have long since been 

 followed in some of our Dominions. 



Another direction in which the work of the Survey could with advantage be 

 extended is in the execution of deep borings ' on carefully -thought-out schemes 

 by which a maximum of information could be obtained. Both in Holland and 

 Germany bbrings have been carried out to discover the nature of the older 

 rocks beneath the Secondary and Tertiary strata, and Prof. Watts, in his 

 Presidential Address to the Geological Society in 1912 (Proc. Geol. Soc. 

 pp. Ixxx.-xc), dwelt on the importance of exploring systematically the region 

 beneath the wide spread of the younger rod^s that cover such a great extent 

 of the east and south of England. Prof. Boulton, my predecessor in this 

 Chair, has endorsed this appeal, but nothing has been done or is apparently 

 likely to be done in this direction. It seems extraordinary that no co-ordinated 

 effort should have been made to ascertain the character and potentiality of 

 this almost unknown land that lies close beneath our feet and is the continiiation 

 of the older rocks of the west and north to which we owe so much of our 

 mineral wealth. It is true that borings have been put down by private enter- 

 prise, but. being directed only by the hope of private gain and by rival interests, 

 they have been carried out on no settled plan, and the results and sometimes the 

 very existence of the borings have been kept .secret. The natural consequences 

 of this procedure have been the maximum of expense and the minimum of 

 useful information. 



Unfortunately in recent years percussion or rope boring, which breaks up the 

 rock into fine powder, has more and more, on account of its cheapness, replaced 

 the use of a circular rotating drill which yields a substantial cylindrical core 

 that affords far more information as to the nature of the rocks and the geological 

 .structure of the district. If private boring is still to be carried on, the adoption 

 of the latter procedure should be insisted on, even if the difference of cost has 

 to be defrayed by the Government. It is quite true that a considerable amount 

 of useful information can be collected by means of a careful microscopic examina- 

 tion of the minute fragments which alone are available for study, so that the 

 nature of the rocks traversed can be recognised ; but the texture of the rock is 

 destroyed, as well as any evidence which might have been available of its 

 larger structures and stratigraphical relations and almost all traces of fossils. 

 It is, too, impossible to tell with certainty the exact depth at which any par- 

 ticular material was originally located, for fragments broken off from the sides 

 of the bore may easily find their way to the bottom. 



A good illustration, and one of manj'' that might be cited, of the misdirected 



° I have not space to deal here with the shallow borings in soft strata which 

 have been so successfully conducted on the Flanders front during the war by 

 Captain W. B. R. King, of the Geological Survey. Similar borings have been 

 already carried out by the Survey on a limited scale, but in the light of the 

 experience that has now been gained we may look for a widely extended use of 

 the method both by private workers and by the Purvey officers. 



