310 Prof. Horsford on the Permeability of Metals to Mercury. 
tity transmitted in a given time, soon attained a maximum from 
which it varied but little to the close of the experiment.* | 
The 5th, 6th, 7th, Sth, 12th, 13th and 14th weighings gave 
quantities varying but little from each other. The 9th exceeded 
any of the preceding determinations so much that I was led toa 
careful inspection of the circumstances attending the experiment. 
I found the bar more deeply immersed in the mercury. Its posi- 
tion was maintained for the two succeeding experiments, and then 
changed to that oceupied at first. These weighings led to the opin- 
ion that the cause of the discrepancy was the unequal absorbing 
surface, to which the mercury had been exposed. More mercury 
had passed into and through the bar in one case than the other. 
This view was confirmed by an especial experiment to ascertain 
VI. What is the influence of the extent of absorbing surface 
exposed to the mercury ? 
Two bars of equal length and diameter were taken. They 
were bent into syphons and the shorter leg dipped in a solation 
of gutta percha in chloroform—a sort of collodion which 1n- 
crusted them with an impermeable envelope. After drying, the 
gutta percha cuticle was scraped from the eud of one bar—ab 
from the end and nearly an equal portion of the side of the other. 
The shorier legs of both were placed in the same cup of mer- 
cury and the longer legs in other weighed cups. 
‘I'wo drops fell from the bar haviug the larger surface before 
any fell from the other. After nine days the quantities were 
weighed. ‘Through the bar having the greater absorbing surface 
there had flowed, . : . 38902 gr. 
_ Through that having less, . , 2-1285 “ 
It might be supposed that the syphon action would be limited 
by the height to which the mercury rises in a vertical bar. A 
experiment was made to ascertain 
ry 
A bar was saturated with mercury and then bent into the form 
of a syphon—the shorter leg being 0-150 mm.—the longer 0-800 
dropped from the longer leg. As the bar was saturated. with 
mercury, the height to which the latter metal rose in the syphoa 
* Experiments undertaken since this paper was sent to'the Journal, show that the 
above conclusions may require some modification, At the close of the above series 
of experiments, the quantity of mercury passed in 5 days was a fraction less t 
32 grammes. At this stage, the surface of the bar-syphon was rubbed so as to - 
3 esent a continuous amalgam. Thereafter the 
flow of mercury ray idly increased, until at the date of this note (March 8) @ bar- 
pa less than 0006 mm. in diameter and 0-070 mm. kc discharges in 24 hours, 
extraordinary quantity of 40° grammes. : 
