In PERTHSHIRE. 245 
rection from their centre. They are commonly obferved at 
Lawers on the eaft ; throughout the whole of Glen-Leadnach, at 
Dunira, Dalchonzie and Aberuchill, on the north and weit ; and: 
do not reach fo far as the man/fe, which is about three quarters | 
of a mile on the fouth of Comrie*. 
I am, with great regard, 
DEAR Sir, 
Your’s moft fincerely, 
RALPH TAYLor. 
Pema eos iG. Rk P ST 
Dudding fone Houfe, Fan. 24, 1793. 
THERE is no reafon to believe, that thefe phenomena are yet 
come to an end. After temporary intermiflions, fometimes of 
feveral months, they have returned, ever fince their firft ap- 
pearance in 1789, without any apparent “wed ear in their 
extent 
* Tur traét within which the concuffions deferibed in this letter appear to have been 
confined, is a {pace of a reftangular form, which extends from eaft to weft along the north 
fide of the Earn about 22 miles in length, by a lictle more than five in breadth; reckon- 
ing the utmoft length from about Monzie to the head of Loch Tay, and the breadth 
“from a little fouth of the Earn nerthward to the ridge which feparates the branches of 
that river from thofe of the-Almond. The whole-of this tra¢t is mountainous, except 
toward the eaftern extremity, where it joins the low country, and on the banks of the 
river Earn on the fouth. It is interfe¢ted by narrow glens or valleys, the moft confider- 
able of which is Glen-Leadnach, where the centre of the concuffions feems to be placed. 
The mineralogy of this part of the country has not hitherto been accurately examined ; 
but it is known ia general, that the ftone is the. primary fchiftus, and in fome places 
granite ; that no mineral veins, nor any hot fprings, have been found in it, and that no 
volcanic appearances have been obferved. In the, valleys, among the mountains, iron 
ore, of the kind that is called bog ore, is faid toabound. Dr Hurvon has remarked, that 
the line which terminates this tract on the S. E. feems to be nearly the fame with that 
_ where the primary ftrata fink under the furface, and are covered by the fecondary, or 
horizontal ftrata. J, P. 
