132 Mr. Rennie’s account of experiments 
No. specific gravity. 
lbs. avoir. 
125 Craig Leith with the strata 
2.452 
15560 
126 Devonshire red marble, variegated 
16712 
127 Compact limestone 
2.584 
1 7354 < 
128 Peterhead granite hard close grained 
18636 
129 Black compact limestone, Limerick 
2-59 8 
19924 
130 Purbeck 
2-599 
20610 
131 Black Brabant marble 
2.697 
20742 
132 Very hard freestone 
2.528 
21254 
133 White Italian veined marble 
2.726 
21783 
134 Aberdeen granite, blue kind 
2.625 
24556 
N. B. The specific gravities were taken with a 
l delicate 
balance, made by Creighton of Glasgow, all with the ex- 
ception of two specimens which were by accident omitted. 
Remarks. 
In observing the results presented by the preceding table, 
it will be seen that little dependence can be placed on the 
specific gravities of stones, so far as regards their repulsive 
powers, although the increase is certainly in favour of their 
specific gravities. But there would appear to be some unde- 
fined law in the connection of bodies, with which the specific 
gravity has little to do. Thus, statuary marble has a specific 
gravity above Aberdeen granite, yet a repulsive power not 
much above half the latter. Again, hardness is not altoge- 
ther a characteristic of strength, inasmuch as the limestones, 
which yield readily to the scratch, have nevertheless a repul- 
sive power approaching to granite itself. 
It is a curious fact in the rupture of amorphous stones, that 
pyramids are formed, having for their base the upper side of 
the cube next the lever, the action of which displaces the 
