Remarks on the Transition Rocks of Werner. 99 
“whose uniformity is occasionally interrupted by small 
isolated hills, like islands ina lake. These are pro- 
bably formed of Transition rocks, although on the 
plain itself, where the soil is laid open, which is prin- 
cipally composed of limestone debris, horizontal strata 
of the same substance were exposed to view. Ap- 
proaching Taunton, the road leads over some of these 
No. hills, and here it was that I met with strata highly in- 
1, 2. clined, very similar in colour and aspect to some va- 
rieties of sandstone, but considerably more refractory 
under the hammer, indicating, I suspect, the com- 
mencement of the Transition series, 
3. VEsicuLar Trap. I found this on the road near the 
house of Sir Thomas Acland, a few miles north of 
Exeter. I saw none of this in situ, though very 
commonly in the buildings in and about Excter, 
4. On guitting Exeter for Moreton, the road is extremely 
hilly, rising: and descending over abrupt knolls al- 
most all the way ;. these are principally formed of a 
soft decomposing rock, in thin strata, breaking in 
thomboidal fragments, and very similar to the slaty 
clay of Werner, 
5,6,7.After passing Teign Bridge, this substance assumes a 
greater decree of consistence, and occurs in strata 
nearly vertical, some of which are coarser in the 
grain than others. These were extremely difficult 
to break, and presented a close smooth fracture, ap- 
proaching to conchoidal. 
8. The Teign is the eastern boundary of Dartmoor, and 
within a few hundred yards of it, and immediately 
beyond the stratified rock last mentioned, Granite 
occurs, containing very large crystals of felspar, 
which continues to within a short distance of Ta~ 
vistock, situated on the Tavy, which bounds Dart- 
moor on the west side. 
Here, as on the bauks of the Teign, the Killas rests 
upon the Granite. At Wheal Friendship, a mine 
at that time under the management of Mr. John 
Taylor, (to whose intelligence I am deeply indebted 
for a great share of the information I obtained in 
the country,) I selected the following specimens, as 
illustrative of the Cornish terms, which certainly 
afford the best explanation that can be given, of a 
language entirely peculiar, 
9. Killas, by comparison with the Grauwacke Slate of 
Freyberg. I find this to be quite as similar as any 
Ge two 
