F. P. Mennell — The Northern Margin of Dartmoor. 419 



secondary axinite along its margins. The beds above the chiastolite 

 band do not cross the river in this neighbourhood, owing partly to the 

 direction taken by the stream, and partly to the fact that the strike 

 swings round somewhat to the north, so that the representatives of 

 the beds numbered 9 and 11 in the Okement section are here right 

 outside the aureole of metamorphism, and it is therefore difficult to 

 identify or define them with any certainty. West of Sticklepath 

 there is still another band of epidiorite above the cordierite hornfels. 

 Then follows limestone, chiefly altered to a yellowish garnet rock, at 

 one time worked for copper with some success at the Belstone mine. 

 Beyond, indications of contact alteration are absent, and the exposures 

 are so poor that it is difficult to determine where any of the upper 

 beds cross the Taw. The rock burnt for lime near South Tawton is 

 very possibly the unaltered continuation of the metamorphosed upper 

 limestone. It may also perhaps be identified with the limestone 

 formerly worked for lime in the quarry at Drewsteignton, whicli is 

 said to be fossiliferous. The lower limestone bed has been actively 

 worked for copper in the Kamsley mine at South Zeal. It has been 

 converted into black' garnet rock for the most part, but other very 

 interesting types are to be seen. One of these is a garnet- augite- 

 axinite rock in which the garnets show the most remarkable examples 

 of zoning that I have ever seen. This "calc-flinta" probably 

 corresponds with that which is still worked for road-metal further east 

 at Nattenhole Quarry, where the more crystalline bands consist of 

 a very interesting augite-axinite rock containing some felspar. 



The andalusite hornfels is seen in a fresh condition along the stream 

 running through Ford Farm, where there are some small openings 

 made to obtain building stone. The rock is interesting petro- 

 graphically from the fact that it is here a biotite-andalusite hornfels, 

 whereas further west it is muscovite-bearing. The exposures have 

 revealed from time to time the presence of numerous veins emanating 

 from the granite varying from several feet to a fraction of an inch in 

 width, and containing visible pink crystals of derived andalusite. 

 The lower "calc-flinta" has also been exposed in a prospecting 

 shaft (said to be for arsenic) at Ford Farm. In addition to the usual 

 silicates, sections from this locality sometimes show a very strongly 

 birefringent mineral, which is no doubt datolite. The tuff seems to 

 die out in the neighbourhood of Sticklepath. All the rocks are 

 poorly exposed beyond South Zeal, and I have not attempted to trace 

 the various beds beyond that village. 



III. "Westward Continuation of the Series. 

 West of the Okement the beds are not at first very easy to follow. 

 Near Okehampton fragments of tuff and epidiorite are to be found in 

 abundance on the golf links, but it is not easy to say where they 

 occur in situ except that there is an outcrop of epidiorite just below 

 the Artillery Camp. A number of narrow seams of garnetiferous rock 

 with shale partings pi'obably represent the upper limestone, and are 

 well exposed at the Camp Hill Quarry. These dip south and thus 

 indicate a sharp local synclinal fold. Both red and black garnets are 

 present, and these are embedded in a matrix which is sometimes 



