82 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JunC 13, 



and agrees with the distances given below, the results of a number of 

 lines of soundings derived from charts. The inference we must derive 

 fi'om this is, that extended lines of deposits, having an uniform mi- 

 neral character, must have had at their periods of deposition a certain 

 parallelism with the coast-lines of their seas. 



§ 3. The necessary and ob\^ous result of a process of accumidation 

 where the quality of the sea-bed is dependent on depth and distance, 

 and where the progress of the several zones of materials is outwards, 

 will be, that in process of time each distinct zone of mineral matter 

 will overlap the one immediately in advance of it. A deep sea channel 

 thus filled up would present, in the long vertical sections through its 

 bed (which is the manner in Avhich we look at ancient sea-beds), a 

 gradual change in mineral character ; the tenacious mud would pass 

 into fine silt and ooze — the original deep water beds ; after a cer- 

 tain amount of accumulation, these would be surmounted by the sands 

 of the next zone of depth, a progressive increase in the coarseness of 

 this arenaceous series would be obsei"\^able ; lastly, the coarse ground 

 zone would be found running out and restmg on that of clean sand : 

 throughout the series, taken as a whole, there would be a regular 

 order of superposition. If we imagine a sea-bed, a b, thus accumulated, 

 to be subsequently raised to an uniform level, without any reference 

 to the former depths of deposition, just as the deposits of the se- 

 condary and tertiary periods mostly are at present, and be made to 

 exhibit a section at right angles to its coast-hne, we should have, first, 

 such a succession as represented fig. 2 ; and which if described in 



Fig. 2. 



Argillaceous beds. Sand and sandstone strata. _ Gravel beds. 



m 



' clean and shell sand, small pebbles. Shingle banks. 



I, Deep sea mud. 



the ordinary language of geology would be — a thick ascending series, 

 commencing with clays and marls, or pure limestones, according to 

 the preponderance of the remains of animal life (Zoophytes, MoUusks) 

 over that of the mineral masses on the coast-line, passing up into and 

 succeeded by a vast accumulation of sand, and finally surmounted by 

 coarse beds of gravel and shingle : concurrently with this mineral 

 change, there would be another as great in the suites of animal re- 

 mains, if we confined ourselves to such as should indicate that they 

 had lived at the places where they might occur. 



With respect to the finer and more distant sedimentary beds, the 

 change upwards in mineral character would be progressive ; whilst in 

 other cases, and nearer the coast-hne, where an accumulation of sand 

 or gravel might have travelled out mth a diagonal arrangement over a 

 previously formed sea-bed, the line of separation might be very de- 

 fined, or as we should say geologically, the mineral character would 

 change suddenly. All these appearand might be presented, and yet 

 not warrant the supposition, of any violent physical change ; the sea- 

 bed of this and of every past period must be considered as a syn- 



