722 Mr. Lonsdale on the Age of the 



Maton notices the South Devon limestones and places those on the eastern side of the Tavey 

 in argillaceous slate ; but in his geological map the same character is employed for the Devonshire 

 limestones, the mountain limestone and the oolitic series. (Tour through the Western Counties, 

 vol. i. pp. 121, 289,290, 1797.) 



Playfair notices a bivalve shell which he found in a loose specimen of schistose micaceous lime- 

 stone opposite Stonehouse ; and he adds, there are certainly no rocks more decidedly primary than 

 those which surround Plymouth. He considered the limestones of Berry Head to be of the same 

 age. (Illustrations of the Huttonian Theory, note iv. p. 1 64, 1 802, French Translation, p. 54, note.) 



In 1809, Dr. Berger and M. Louis Albert Necker made their joint examination of Devon- 

 shire and Cornwall ; and they both considered the limestones to be transition. They observed no 

 organic remains. (Dr. Berger, Geol. Trans., 1st Series, vol. i., p. 103. 1811. Necker, MS. Catal.) 



De Luc mentions frequently the Plymouth, Chudleigli, and other limestones of Southern Devon ; 

 and describing a quarry near Sequer's Bridge, he says, " The strata much resemble the most ancient 

 secondary limestones of the Alps, which contain but very few marine bodies." He observed none 

 in that quarry. (Geol. Travels in England, vol. ii. p. 342 ; see also Index to vol. xi. 1811.) 



Dr. Thomas Thomson assigned the Plymouth limestones to the transition class. He sought 

 likewise carefully for fossils, but equally without success. (Ann. of Phil., vol. ii. p. 248, 1813.) 



Dr. Kidd placed the Devonshire marbles in the transition limestones of Werner, including in 

 them the mountain-limestone. (Geological Essay, pp. 93, 94, 1815.) 



In Mr. William Smith's map of England (1815), the limestones are coloured as portions of the 

 transition series. 



Mr. Brande, in his Outlines, considers the Plymouth calcareous rocks as mountain-limestone, 

 and states that they rest immediately upon slate. (Outlines of Geol. p. 90, 1817.) 



The late Mr. W. Phillips assigned them to the transition series. (Outlines, 1st edit. p. 210, 

 181C; Selection of Facts, p. 162, 1818.) 



In Mr. Hennah's first notices on the organic remains of the Plymouth rocks, the age of the 

 strata is not defined ; but it is impossible to pass over the first communications of a geologist to 

 whose labours we are indebted for a large share of that evidence by which the classification of the 

 Devonshire formations will be decided. (Geol. Trans., 1st Series, vol. iv. p. 410, 1817.) 



In Mr. Greenough's First Principles of Geology, (p. 219) published in 1819, the Plymouth 

 calcareous rocks are noticed as examples of mountain limestone, resting immediately upon slate, 

 to the exclusion of the old red sandstone ; but in the first edition of his geological map (1820) the 

 whole of the South Devon limestones are coloured as belonging to the grey wacke series. 



In a memoir on Cornwall, Professor Sedgwick, in alluding to Mr. Hennah's collection of organic 

 remains, states his belief that the fossils cannot be identified with those of the mountain-limestone; 

 and he adds, " It would introduce great confusion not to separate the limestones of Devonshire 

 from the great metalliferous limestones." (Trans. Phil. Soc. Cambridge, vol.i. p. 142, 1820, 1821.) 



The Rev. W. Conybeare, in his Outlines (p. 353, 1822), and in his memoir on the mountain 

 chains of Europe, (Ann. Phil., vol. xxi. p. 7, 1823) and Dr. Buckland in his description of tlie 

 caves at Oreston and the fissures at C\mi!i\e\^\{Reliquice Dil., p. 59, note e. 1823), consider the 

 South Devon limestones as transition. 



The Rev. J. J. Conybeare assigned the dark limestones to his " superior slate," and the coral 

 limestones to his " sand slate " division. (Ann. Phil. 1823, vol. xxi. p. 185.) 



MM. Dufrenoy and Elie de Beaumont, who visited England in 1823, place them in the grey- 

 wacke series. (Voy. Metal, p. 11, 1824.) 



About the year 1824, Mr. Hennah published his account of the limestone rocks of Plymouth ; 

 and considered them, on account of the abundance of their organic remains, to be " among the 



