56 
MR, H. TOMLINSON ON THE INFLUENCE OF STRESS 
fastened to a very fine platinum wire, so that the pieces could be weighed in air and 
in water. 
It should be stated that carbon in this form being porous, the specific gravity as 
usually reckoned will be found to increase if the substance be allowed to remain in 
water for any time, and especially so if the carbon be boiled in water. The following 
experiment will show the extent of alteration of the apparent specific gravity :—- 
Experiment XI. 
Several pieces of carbon tied together with fine copper wire, and boiled for five 
minutes; the jfieces then taken out of the hot water, kept for five minutes in cold 
water, and afterwards suspended by a fine platinum wire in a large vessel filled with 
water at 15° C. 
Weight of carbon 
in water. 
Time after immersion in 
the large vessel 
of water, at 15° C. 
4-800 
5 minutes. 
5-020 
15 „ 
5-140 
35 
5-255 
< 5 ,, 
5-291 
]40 „ 
The pieces then boiled a second time for 40 minutes, and after having been kept in 
cold water for 30 minutes, again tested for loss of weight. 
Weight of carbon 
in water. 
Time after immersion in 
the large vessel 
of water, at 15° C. 
5-314 
5 minutes. 
5-340 
45 
5-393 
13 hours. 
5-432 
54 days. 
5-452 
12 1 
1 w 2 
As the temperature of the water varied very little during the periods of observation, 
we see that the apparent specific quantity went on increasing for more than 12 days, 
and that the total percentage of increase amounted to nearly 12. The specific 
gravities, however, recorded in the table are calculated from the loss of weight observed 
shortly after immersion in water, the pieces of carbon not having been boiled, and the 
section as determined by dividing the loss of weight by the length agreed very well 
with the section measured by the wire-gauge. 
With the exception of number 5, the value of “ Young’s modulus ” increased very 
