94 



SCIENCE-GOSSIP. 



GEOLOGY 



CONDUCTKD BV EDWARD A. MARTIN, F.G.S. 



BovEV Tracey Beds. — Opinion is still divided as 

 to whether these beds should be placed with the 

 Eocene or Miocene formations. The)' consist of 

 sands, clays and lignites, deposited in a plain, stretch- 

 ing from north-cast to south-west for a length of six 

 miles, and having at its broadest part a width of four 

 miles. This plain follows the course of the united 

 Teign and Bovey rivers, and is surrounded on all sides 

 by lofty hills ; the granite heights of Dartmoor over- 

 looking the plain on the west and north-west. The 

 beds appear to ha\e been laid down in a lake, formed 

 by an expansion of the t\\ o ri\ers. Bovey coal has 

 been worked since 1714. The clay beds have been 

 largely worked for pottery at Newton Abbott and 

 Kingsteignton. Mr. J. Divett found that the lignite 

 beds were cut off by a fault from the cla\- beds, giving 

 a vertical displacement of not less than 100 feet, the 

 lignite being probably the upper series. The total 

 thickness is conjectured to be from 200 feet to 300 

 feet. The beds were originally placed in 1863, by 

 Messrs. Heer and Pengell)', with the Miocene. This 

 reference has been questioned by Mr. Starkie Gardiner, 

 who thought they corresponded with the Middle 

 Bag.shots, or the Bournemouth leaf-beds, and classed 

 them as Upper Eocene. Pengelly stated that 

 wherever the Hempstead Beds of the Isle of Wight 

 are finally placed, there must also be the Bovey 

 Tracey beds. The Hempstead Beds are now assigned 

 to the Oligocene series, and presumably the Bovey 

 Tracey must be also. With this classification, the 

 Miocene age is unrepresented in England. Out of 

 the seventy-two separate layers which were mapped 

 out by Heer and Pengelly, only fifteen were found to 

 contain fossils, viz., two of clay and thirteen of 

 lignite. The fossils consisted of ferns (Pecop/eris 

 ligniliim and Last-raea stiriaca), with twigs, leaves, 

 and debris of Setjtioia coiittsiae. In the twenty-sixth 

 bed from the top, there was an abundance of seeds of 

 various kinds, including those of the gardenia. In 

 the fourth bed, Heer discovered a single specimen of 

 ' Buprestis falconeri. In the 17-feet bed, were found 

 Cinnainoinum scheuchzen and C. lanceolatiiin . 



Formation of "Paper" Strata. — When 

 walking along the shore recently between Shanklin 

 and Luccombe, Isle of Wight, I was much interested 

 in watching an operation which shows how a series ot 

 thin alternate layers of sand and clay may occur in a 

 formation, each alternation of which may be due to a 

 separate cause. The Lower Greensand cliffs there 

 are partly clay and partly sand, with every conceivable 

 gradation between the two. Water is constantly 

 oozing out at various levels in the cliffs, and as a 

 spring proceeds down the face of the clifls it carries 

 with it a good deal of .sand in suspen.sion. The face 

 of the cliff being very irregular, the velocity of the 

 fall is frequently checked, or the water sinks out of 

 sight, with a result that it deposits mud all along its 

 track. If the water had flowed in some quantity, and 

 the supply had given out, then that which remained 

 carved out a second cour.se in the centre of the original 

 mud-stream. Finally reaching the sand at the foot of 



the cliff, springs had, in many instances, given rise to 

 small streams, which, although at first sinking through 

 the sand, in the course of a few hours had given rise 

 to deltas, extending from four to five feet away from 

 the cliff, ori the surface of the sand. The stream 

 di\-ided off into a dozen small branches, having given 

 rise to as man)- bounding banks of mud, in the centre 

 of which was each miniature stream. They were, to 

 all intents, like so many miniature Mississippi deltas. 

 Scraping awa)- carefully some of the mud, a la)-er of 

 sand was found immediately beneath, which had been 

 brought up h)- the previous tide. Below this biscuit- 

 like layer of sand was another similar layer of delta- 

 mud, which had been brought down from the cliff in 

 the interval between the two previous high tides. 

 Here, then, was an interesting example showing tlie 

 alternate deposition of sand and clay, the former 

 brought in by the sea, the latter being due to sub- 

 aerial denudation of the cliff. The thickness of the 

 la)-ers of mud would depend on the strength of the 

 flow of freshwater springs. In a spell of dry weather, 

 water would not issue so prolifically from the cliffs, 

 and if the)- reached the base at all, would cause the 

 deposition of but thinner layers of mud. To add to 

 the resemblance between these layers and some of the 

 older strata, the marks were distinct upon the mud, 

 where a small crab had wandered aimlesslv across and 

 around the "delta," generally in circular fashion, 

 with his footprints constantly crossing and recrossing 

 one another. 



Complex Shell Deposits. — It is sometimes 

 difficult to understand the assemblage of freshwater 

 and saltwater shells in one and the same deposit. In 

 rounding the point between Totland Bay and Colwell 

 Bay, in the Isle of Wight, I picked up at random a 

 handful of the beach near the foot of the clifl^s. In it 

 was found shells of the genera Liinnaen. Plaiwrhis 

 Cerilhium, and Natica from the Headon Beds, which 

 are partly of freshwater and partly of saltsvater 

 origin ; also N'assa, cast up by the present sea : Helix, 

 of two species, from the fields above. Let this beach 

 be subjected to an indurating process, and it would in 

 ages to come be not altogether eas)- to account for 

 its origin. Some geologist of tlie future might ask, 

 " was it of freshwater or saltwater origin, and to what 

 age did it belong ? '' 



Mutton's " Theory of the Earth."— Vol- 

 ume HI. of James Mutton's "Theory of the Earth" 

 has been published by the Geological Society, under 

 the editorship of Sir Archibald Geikie, D.C.L. 

 F.R.S. The first two volumes were i.ssued in 

 1795. In the interesting preface by the present 

 editor, we learn that the MSS. now published had 

 been for more than forty years in the possession of the 

 Geological Society. After Mutton's death, in 1797, it 

 passed into the hands of his biographer, Playfair, and 

 afterward into those of Lord Webb Seymour, who 

 referred to it in 1S14 as being "nearly ready for the 

 press." On the death of the Tast-mentioned, it passed 

 to Mr. Leonard Horner, who gave it to the society in 

 1856. Although the pre.sent volume is mainly inter- 

 esting from a historical point of view, it is of 

 additional importance in that, as Sir Archibald shows, 

 it reveals Dr. Hutton as an enthusiastic worker in the 

 field, and as a most diligent observer ; removing the 

 reproach of his lifetime that he was a mere theorist. 

 " It seems but a tardy act of justice to his fame that the 

 merit of this practical side of his life-work should be 

 now at last fully established." The book consists of 

 267 pages, and the editor has added a most useful 

 index, not only to the present volume, but to Volumes 

 I. and II. also. 



M.: 



