SKETCH OF JOSEPH PRESTWICH. 257 



the catchment basin controlling the volume of the rivers was large, 

 and where permeable strata prevailed. Thus it was with London, 

 and the extension of that city had worked along in those directions 

 where water was got with the best facility. The second part of the 

 address related to the work of the Royal Commission to examine 

 into the coal fields and the coal supply, under which Dr. Prestwich 

 was charged with the study of the districts covered by the later 

 Secondary and the Tertiary strata, with the special object of inquir- 

 ing "into the probability of finding coal under the Permian, new 

 red sandstone, and other incumbent strata. The discussion of this 

 subject implied a survey of the coal fields of England, France, and 

 Belgium, and the possible connection through strata underlying the 

 formations named. Several regions were indicated where trials for 

 coal might be made, which it was admitted, however, might be at- 

 tended with considerable uncertainty. But whether successful or 

 not as to coal, such trials near London could hardly fail of some im- 

 portant results; for it was "possible that the lower greensands 

 would at some spots be reached, so that the inestimable additional 

 benefit of a large and steady supply of pure water might also be 

 obtained, and with proper care to prevent interference might be 

 maintained for all time." 



Commending Dr. Prestwich's investigation of the sources of the 

 water supply of London, and the presentation of the results in his 

 book on that subject — " a masterpiece of minute observation and 

 close and accurate reasoning " — Prof. J. ~W. Judd observed that the 

 geologist could point to the work " with pardonable pride as afford- 

 ing convincing proof that his science has now acquired a character 

 for exactness analogous to that which is justly regarded as the crown- 

 ing attribute of astronomy." His predictions as to the finding of 

 coal underneath the Secondary rocks across the kingdom were like- 

 wise justified in the results of borings made near Dover. 



An important practical application of Dr. Prestwich's investiga- 

 tions of the geology of the English Channel, not anticipated when 

 they were begun, was illustrated in his report on the subject to the 

 Institution of Civil Engineers, presented in December, 1874. This 

 report was described by Nature as being a most excellent example 

 of the indispensability of thorough scientific research as a basis for 

 the useful arts, and of the way in which the highest practical results 

 unwittingly follow from such investigations — made in abstract in- 

 quiry, the only end of which was thorough knowledge of the sub- 

 ject in all its scientific aspects and relations. This study of the 

 strata underlying the Channel — an almost perfect example of close 

 and careful reasoning on physical facts — was now brought forward 

 to enlighten the projectors of a tunnel between England and France 



VOL. LII. — 21 



