fome Strata in Ireland and Scotland. * 99 
h have been abfolutely funk and fwallowed into the earth, at 
4C fome remote period of time, and became the bottom of the 
“ Atlantic Ocean. A period indeed much beyond the reach of 
44 any hiftorical monument, or even of tradition itfelf.” 
That you may more readily compare the fpecific gravities of 
the llay lavas, and other fubftances (mentioned in thefe letters) 
with thofe from other parts, I have annexed a table of their 
feveral weights ; and remain, &c. 
A . 
MILLS. 
Ardlun Coal, - 
- I ? 284 
Jet, according to Dr. Watson, 
•as 
1,236 
• l,l80 
Cannel coal, from Haig in Lancafhire, 
*>275 
Whyn Dyke, from near McArthur’s 
head, N° 1 
. 2,863 
Whyn Dyke from Freeport, infide 
N° 2. 
2,88 1 
outfide 
3- 
2,850 
Whyn Dyke from Gartnefs, N° 4. 
m 
2,631 
5- 
- 
2,698 
6. 
- 
- 2,484 
7* 
■1 
2,542 
a. 
«p 
2,322 
9- 
•» 
1 
bi 
V* 
00 
Co 
10. 
m 
2,652 
Bafaltes from the Giant’s Caufeway, 
ate 
2,743 
from Fairhead, 
tsa 
* 2,950 
— from Ardlun, 
m ®a 
2,724 
— from Staffa, 
* « 
2,736 
O 2 
Vitrefcent 
