JET. 73.] ORIGIN OF FLINTS. 323 



it gave the chemical analyses of the various samples 

 of river and other waters by leading analysts. His 

 investigations had been again of use to the University. 

 The next memoir, sent to the Hoyal Society in the 

 end of March, was " On the Agency of Water in 

 Volcanic Eruptions, with some Observations on the 

 Thickness of the Earth's Crust from a Geological Point 

 of View, and on the Primary Cause of Volcanic 

 Action." This was published in 1886. The hypothesis 

 put forward was an interesting one to geologists. 



A stay at Weston-super-Mare early in April was 

 refreshing its main purpose being the acquisition of 

 material, in the study of raised beaches, for his pro- 

 jected Submergence paper. But the weather after a 

 fortnight became unseasonably cold, and the sojourn 

 there was not prolonged. 



The origin or segregation of flint was a subject to 

 which he gave much thought ; but the experiments 

 which he was carrying on in the Oxford Museum, in 

 a series of jars of fresh and of sea water, were extended 

 over too short a term of years to yield definite or 

 satisfactory results. These experiments were begun 

 in 1882, with pure precipitated chalk dissolved in 

 dilute hydrochloric acid, and the results are recorded 

 at intervals in a book in his handwriting. Pieces of 

 sponge, or small cup-sponges, empty shells and frag- 

 ments of wood, &c., had been added to the contents 

 of the jars, half of which contained sea - water, the 

 other half fresh-water. An entry dated 24th June 

 1884 registers "Sponge rendered brittle- requires ex- 

 amination for silica." In the same MS. book of notes 

 we find a series of experiments registered on " Ayles- 

 ford sand with Woolwich flint pebble moistened with 

 a solution of soluble silica." 



