114 
DE. JOULE ON SOME THEEMO-DYNAMIC PEOPEETIES OF SOLIDS. 
Table (continued). 
Remarks on the condition of 
the wood. 
of rod 
per foot 
in 
grains. 
Dried still further 231*5 
Water poured between the 
glass tube and the rod. 
Then after a short time . . . 
After ten mimites more had 
elapsed 
After another ten minutes . . . 
After another ten minutes ... 
After another ten minutes ; I 272-3 
sp. gr. ‘5646 
Dried some hours in a mode- I 
rately heated oven 
Immersed in oil under the 
exhausted receiver of an J- 329 
air-pump 
Extreme 
length 
in 
inches. 
Medium of 
communica- 
tion of heat 
between the 
glass tube 
and the rod. 
Tension 
in 
pounds. 
Limits of tempera- j 
ture between which 
the experiments | 
were made. 
! 
r 
Linear contrac- j 
tion or expansion 
jer degree Centi- 
grade. 
r dung’s modulus, 
of elasticity or 
length of rod, 
weigMng 1 lb. per 
'oot, which would 
)e extended unity 
by 1 lb. tension. 
16*48 
Air 
4*3 
37*7 and 10*24 
•000084212 E. 
96170 
Water ... 
4*3 
37*2 and 10*3 
*000058836 E. 
82430 
Water ... 
4*3 
40*9 and 12*15 
*000019457 E. 
Water ... 
4*3 
37*6 and 12*3 
*000004815 E. 
Water ... 
4*3 
42 and 12*3 
•000001017 c. 
r Water ... 
4*3 
39*34 and 12*53 
*000002951 C. 
1 6*656 
"[Air 
4*3 
37*5 and 9*7 
*000000817 C. 
15*55 
Air 
' 4*3 
41*5 and 9‘77 
•000038620 E 
15*54 
I Air 
1 4*3 
38*8 and 10*6 
•000043670 E 
1 
1 
1 
74. The specific gravity of the wood, considered apart from the aii or water in its 
pores, was in the above specimen found to be 1-595. 
75 The following are deductions from the above experiments : 1st. That tension 
increases the expansibility of wood by heat. 2nd. The expansibility of dry wood cut 
across the grain is about ten times as great as its expansibility when cut m the direction 
of the grain. 3rd. The length of wood cut longitudinally is a little mm-eased b> the 
absorption of water; but when cut crossways, a very great augmentation, as is well 
known, takes place. 4th. When water is absorbed into the pores of wood cut longi- 
tudinally its expansibility decreases, until ultimately it passes into contraction by lieat. 
5th. When water is absorbed into the pores of wood cut across the gram, its expansibility 
appears to increase in the first instance, then decreases until it changes mto contracUon, 
which, after increasing with the absorption of water to a certain point, seems to dimmish 
as the wood becomes completely saturated. 6 th. Cut lengthways, the elasticity o 
appears to be lessened by the presence of water; when, however it is cut across the 
grain, the effect of moisture is very greatly to impair the elastic force, -th. A shor 
period of immersion enables wood cut crossways to take up sufficient water to make 
it contract by heat; but, on the contrary, wet wood partially dried on the surface is 
expanded by heat. So that we may have contraction or expansion of wood charge o 
the same extent with water, according probably to peculiarities iii the distiibutioii o 
the water among the pores. n . • 
76. When wet wood, cut across the grain, is dried, it gets shorter very gradiu y, m 
consequence of a tendency to retain its former dimensions. The strain thus arising may 
be removed by raising the temperature, which speedily reduces the wood to the leng h 
due to its state of dryness. The same kind of effect takes place, but in the reverse 
