ractice this precision is not however 
a as a peppercorn be left, the 
t i. the sensitiveness of his 
lu ll disappear in a few- 
hours by absorbing chlorine. But thisiel to be waited for ; as 
soon as no further rise takes place in a minute or ‘two, the siti 
is to be inclined on one ae and the reside turned o 
open leg. er dette Petia 
_ Now, recurring to iat has been anda on ie equilibrium, it it is” 
iain that this excess of hydrogen arises from a want of chlorine ~ 
in the tithonometric liquid. A proper quantity must therefore 
~ be furnished by proceeding as follows. 
The sentient tube being filled with the liquid by inclination, 
connect the polar wires with pq, as before. ‘These may be call- 
ed generating wires. Allow the liquid to rise in bc, until the 
third platina wire z, which may be called the adjusting wire, is 
covered an eighth of an inch deep. Then remove the negative 
wire from the cup p into the cup 7, and now the conditions for — 
saturating the liquid are complete ; hydrogen escaping away from 
the surface of the liquid at z, and chlorine continually accumu- 
lating and dissolving between x and d. This having been car- 
ried on for a short time, the gas in ad is to be turned out by in- 
clination and the instrument recharged. That a proper quantity 
is evolved, is easily ascertained by allowing total condensation to 
take place, and observing that only a small bubble is left at a. 
It will occasionally happen in this preliminary adjustment, that 
an excess of chlorine may arise from continuing the process too 
long. This is easily discovered by its greenish-yellow tint, and 
is to be removed by inclining the instrument and turning it out. 
Thus adjusted, every thing is ready to obtain measures of any 
effect, there being two different methods by which this can be 
done,—Ist, by continuous observation ; 2d, by interrupted obser- 
vation. 
Of the method of continuous observation.—This is best describ- 
ed by resorting toan example. Suppose, therefore, it is required 
to verify table I, or, in other words, to prove that the effect on the 
tithonometer is proportional to its time of exposure. 
