5S 
140 Expansion and Contraction of Building Stone. 
By the above table, we find, as the combined result of all the ex- 
periments, that ,3708 should be eight hundred and seventeen times the 
common difference ; and hence the common difference for one de- 
gree of Fahr. is .0004538 inch. Now, assuming 94.05 inches, as 
the mean length of the granite, which is sufficiently near, we find 
the linear expansion for one inch of stone for each degree of Fahr. 
.0004538 
to be 9795 
sion would be .0000579 of an inch. By proceeding in the same 
way with the experiments on the other stones, we obtain the follow- 
ing results. 
= .000004825 inch, and for one foot, this expan- 
Common difference in inch-([Common difference in inch- 
MISE ey Maa es for the whole length] es, for one inch for each 
in inches. 
of stone for 1° of Fahr. degree of Fahr. 
Granite, 94.05 .0004538 .000004825 
Marble, 93.44 .0005297 .000005668 
Sandstone, 94.05 -0008965 .000009532 
White pine, - e Sk .00000255 
Hammered copper, - - - -00000944 
To apply these results to the case in question, let us suppose two 
coping stones of five running feet each, to be laid in mid-summer, 
when they have a temperature of ninety six degrees Fahr. ; in win- 
ter their temperature may safely be assumed at zero, so that the to- 
tal variation of temperature will be ninety six degrees; and if we 
suppose these stones to contract towards their centers, which would 
be the most favorable supposition as regards the tightness of the 
joints where a number of these stones are used, the whole length of 
stone put inmotion by a change of temperature would be five feet. 
If the coping be of granite, the distance by which the ends of the 
stones would be separated, in consequence of one degree’s varia- 
tion would be sixty inches multiplied into .000004825 =.0002895 
and for a variation of ninety six degrees, this distance becomes: 
.0002895 x 96 =.027792 inch, giving a crack a little wider than the 
thickness of common pasteboard. For marble this crack would 
have a width of .03264, nearly twice the thickness of common paste- 
board; and for sandstone .054914, nearly three times the thickness 
of pasteboard. ‘These cracks are not only distinctly visible, but they 
allow water to pass freely into the heart of the wall. The mischief 
does not stop here: by this constant, motion back and forth in the 
coping, the cement, of whatever kind the joints might be made, 
would be crushed to powder, and in a short time be totally washed 
by the rains from its place, leaving the whole joint open. 
