C 73 ] 
IX. Some Account of the Strata and Volcanic Appearances in 
the North ^Ireland and Weftern JJlands a/' S cotland. In 
two Letters from Abraham Mills, Efq. to John Lloyd, Efq. 
F. R. S. 
Read January 21, 1790, 
LETTER I. 
DEAR SIR. Fence Houfe near Macclesfield, Jan. 20, 1789® 
Y OUR requeft (hall be complied with ; I will endeavouf 
to defcribe the Whyn Dykes in the ifland of Hay, and 
give you my reafons for fuppofing them to be of volcanic ori- 
gin ; but you muft not expefl a complete and fcientific defcrip-* 
tion from me who am fo little verfed in mineralogy, and have 
fo little leifure to purfue that ufeful and engaging ftudy. 
My engagements in the mineral line were the caufe of my 
going to Ireland in 1787, to infpedt the copper mines in the 
county of Wicklow, whence I proceeded to the county of 
Antrim. 
As I performed my j’ourney through Ireland on horfeback, I 
availed rnylelf of the opportunity that mode of travelling gave 
me, to note the ftrata as I paffed along ; but (hall not trouble 
you with my obfervations till I arrived in the neighbourhood 
of Moneymore, where I firft perceived tumblers of lava; 
from hence by Maghera, Garvagh, Coleraine, Portrufh, and 
Vol. LXXX, ' L to 
