270 H. J. Loice — Devonshire Geology. 



of Dartmoor, we may be led to infer that prior to the production 

 of the Bovey beds a depression was formed in this locality sub- 

 sequently to the destruction of the mass of chalk and a considerable 

 portion of the greensand which there once existed, and that the 

 materials for this deposit were chiefly derived from decomposed 

 parts of the adjoining granite gradually carried down by sti'eams, 

 the quartzose parts forming the sands, the decomposed felspar borne 

 onward to whei'e it could quietly settle and form the clay." ^ 



That is the simple explanation given in 1839 to account for the 

 peculiar clay, sand, and lignite beds of the Bovey area, and it has 

 been confirmed and strengthened by other geologists, particularly 

 Pengelly, who investigated the formation fully and from whose 

 palceontological discoveries therein Professor Heer arrived at the 

 conclusion that the beds were of Miocene age. In most of the 

 students' manuals upon British geology this explanation of the 

 origin and position of these beds is given, and it still holds the field, 

 for in the latest edition (1903) of Professor Archibald Geikie's Text 

 Book of Geology we find them referred to as " a small but 

 interesting group of sand, clay, and lignite beds, from 200 to 300 

 feet thick, which lies between the granite of Dartmoor and the 

 greensand, in what was evidently the hollow of a lake." The lake 

 hypothesis might thus be called the orthodox view, since other 

 suggestions antagonistic thereto have not so far been able to 

 command general attention, much less acceptance. That being the 

 case it might be thought that little service would be rendered by 

 dragging immature views before the public notice ; but the matter 

 has become more involved since the new Geological Survey map of 

 the district in question has been published, inasmuch as the gravels 

 which cap the bordering hills ai"e now coloured the same as the 

 Bovey lake area, thus associating the two as members of the same 

 series which were disassociated by colour and name in the old maps. 



An attempt to trace the steps which have led to this change and 

 to examine the data upon which a new theory is being constructed, 

 may be of interest. 



The following citations are from papers by Mr. J. Starkie Gardner : — 

 " The fossil plant remains met with in the Bournemouth beds, 

 especially those in the marine series, are so strikingly similar to 

 the Bovey Tracey fossils, as to make it clear to my mind that the 

 latter have been wrongly assigned to the Miocene. I believe, in fact, 

 that they are simply an outlier of the Bournemouth series, from which 

 they are but eighty miles distant." * 



"Time has, however, completely refuted upon plant evidence the 

 theory that the Bovey beds are Miocene, and unmistakably identified 

 them with the Middle Bagshot of Bournemouth. Upon geological 

 evidence also the improbability is apparent of such great deposits 

 being accumulated in a Devonshire valley without any trace of them 

 existing elsewhere, and a theory which brings them into a defined 



1 De la Beche : Geol. Report of Cornwall, Devon, and Somerset, p. 257. 

 ' Quart. Journ. Geol. See, 1879, vol. xixv, p. 227. 



