236 
“No. 2. Fou-Rock.—Specific gravity, 2-638 ; a coarse gra- 
nite, which strikes fire under the hammer; it forms a durable 
and strong building stone, and has been employed in the ring- 
stones of Trinity College Belfry, and in the construction of 
the O’Connell Monument at Glasnevin. 
“No. 3. Three-Rock.—Specific gravity, 2652; this gra- 
nite is rather coarse-grained; it was taken from Woodside 
Quarry, on the slope of the Three-Rock Mountain, and, like 
No. 2, has been used in the construction of the O’Connell 
Monument. 
“No. 4. Enniskerry.—Specific gravity, 2-633 ; a rather 
coarse-grained granite, containing veins of black tourmaline. 
“No. 5. Ballyknocken.—Specific gravity, 2:636 ; this gra- 
nite is the best building stone in the neighbourhood of Dublin, 
‘and has been extensively used in the public buildings of this 
city; it forms the principal part of the granite used in the Bel- 
fry and Museums of Trinity College. The quarries are si- 
tuated beyond Blessington, in the county of Wicklow. 
“No. 6. Kilballyhugh.—Specific gravity, 2-616; this is 
a fine-grained granite, and works freely ; it has been employed 
in the construction of the chapel of ease in the town of 
Carlow. ' 
“No.7. Blackstairs.—Specific gravity, 2622; amedium- 
grained granite from Kiltealy, on the Wexford slope of Black- 
stairs. 
“No. 8. Ballyleigh.— Specific gravity, 2°627 ; a fine- 
grained granite, taken from near Poulmounty Bridge, at the 
south-west extremity of the granite chain. 
‘‘ Calculating the atomic quotients from Table 1., we con- 
struct the following Table, containing the values of a, 4, c, 
and of Q, F, M, calculated from equations (1). 
