368 Mr A. J. Avie on the Expansion of Stone 
sorb after having been dried, nevertheless the experiments on 
greenstone show the effect of moisture, and some of the marbles 
certainly became less sensible to the change of temperature, after 
they had been heated, and this was probably caused by their natu- 
ral moisture being driven off. This diminution is distinctly shewn 
by the following series of experiments on Sicilian marble :-— 
Ist, ...... -0325392 : Decimals of an inch for 
ag, 2! 0267163 |" Diff. peep | 23 inches, the change 
Sd, ..<... -0254020' (-~ ‘ ade _ | of temperature being 
Ath, ...... 0240656 J J 180° F. 
The rod gave off a considerable quantity of moisture. This 
gradual diminution of the expansion was scarcely observable in 
the sandstones and Aberdeen grey granite, which contained a 
great deal of quartz; and in the bricks, in the stalk of a Dutch 
tobacco-pipe, and in a rod of Wedgewood’s ware, no such change 
took place, although all these substances had been wet in cutting 
the holes, &c. before they could be put into the pyrometer. ‘The 
Peterhead granite, again, which contains much more felspar than 
that from Aberdeen, and also the greenstone, were affected by 
losing their moisture, but more especially the latter, as shewn 
by the following series of experiments made in November. Un- 
luckily the first observation, which always differs most from the 
others, was lost. 
Dd tere: 0198879 ) Diff, .001'7485 ES of an OS the 
Oliseeats -0180894 0002037 expansion of 23 inches 
Ath, 0.0. 0178857) ates: for 180° F. 
As greenstone absorbs moisture much more readily than the 
marbles, I replaced the rod again in the pyrometer, after it had 
hung in the room for more than three months, from the time of 
performing the first experiments. The instrument was heated 
to 207° F., and this temperature was kept up without change 
during the four hours in which I watched the alterations of the 
