XXXIV PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



he would at such times guide with enthusiastic ardour over the Snow- 

 donian range, pointing out to him from time to time the erratic blocks 

 and marine shells on which he founded his opinion that they were 

 not deposited, as had been supposed, by melting icebergs on the 

 floor of a sea, which after long submergence had been converted into 

 dry land by movements of elevation, but that they were spread by 

 marine currents of extraordinary energy and short duration over the 

 surface of pre-existing land, and over land covered with ice. This 

 opinion, however, he subsequently modified by accepting coast-ice 

 as being probably an efficient agent in these circumstances. 



About the year 1840 he ceased to reside in Wales, and was for 

 some time afterwards employed in the Government Geological Survey 

 of England. He then returned to reside in his native county, Kent, 

 in which he continued until the time of his decease. The last few 

 years of his life were entirely devoted to writing on agricultural sub- 

 jects in connexion with geology, more especially on the drainage 

 of lands, in which he insisted on the following points : — 



1. The important influence exercised by the superficial deposits 

 on the distribution of soils. 



2. The division of those deposits into erratic tertiaries, or Northern 

 drift, and warp -drift. 



3. The division of the erratic tertiaries again into lower and upper 

 erratics, — the lower erratics consisting of boulder- clay, possessing pe- 

 culiar characters found in no other marine strata ; the upper erratics 

 composed of rolled gravel and sand, approaching more the characters 

 of ordinary tertiary strata, but distinguished from them by certain 

 marked peculiarities. 



4. The distinctness of the warp- drift, a deposit which generally 

 forms the surface- soil, and its subsequent origin to that of the erratic 

 tertiaries ; its presence in those districts where the erratic tertiaries 

 are absent, and its diffusion over their denuded surface where they 

 are present. 



5. The indented surface of the beds, whether of the erratic ter- 

 tiaries or of the older strata, on which the warp-drift rests, present- 

 ing a series of irregular ridges and furrows. 



6. The suggestion that the contradictory statements which abound 

 respecting the superior efficacy of deep or shallow drains, of drains 

 at wide or narrow intervals, of drains following the fall of the ground, 

 or crossing it, might perhaps, in many cases, be reconciled by ob- 

 serving whether the drains were parallel or transverse to these 

 natural furrows and ridges. 



Among the numerous publications of Mr. Trimmer may be men- 

 tioned the following, which strongly mark the bent of his mind, and 

 the practical objects he more especially had in view : — 



1. On the Diluvial or Northern Drift of the Eastern and "Western 

 sides of the Cambrian Chain, and on its connexion with a similar 

 Deposit on the Eastern side of Ireland, at Bray, Howth, and Glenis- 

 maule. 2. On the Origin of the Soils which cover the Chalk of Kent. 

 In two parts. 3. Practical Geology and Mineralogy, with an Intro- 

 ductory Discourse on the Nature, Tendency, and Advantages of Geo- 



