Intelligence and Miscellaneous Articles. 545 
proportion as it sinks, and in this way is obtained a continuous cur- 
rent of air through the doors of the iron room towards the suction 
cylinders. But the air cannot reach the suction cylinder without 
first passing through a continuously acting measuring apparatus. 
For this purpose the author selected a large gas-meter, of such dimen- 
sions that 3000 English cubic feet could be measured with it in an 
hour. 
~ . In order to investigate a portion of the air entering by the aper- 
tures in the door and any accidental leakages in the apparatus, 
as well as of the air flowing towards the gas-meter, and to calcu- 
late from the observed difference in the proportion of water and car- 
bonic acid the quantities which had entered from the apparatus, 
there are two aspirators, each of which simultaneously withdraws an 
equal quantity of air. The water of the air is absorbed by sulphuric 
acid and weighed, and the carbonic acid is determined by allowing 
the air to pass in fine bubbles through a determinate quantity of 
lime-water of known strength, and the strength of the lime-water 
finally determined by means of dilute oxalic acid. 
In order to take a specimen of the air remaining in the saloon, a 
forcing and suction pump is connected with the outlet pipe, by which 
flasks holding 6 or 8 litres may be filled with air, and the quantity 
of carbonic acid determined by means of lime-water. The same 
pump serves to determine at any time the variations in the carbonic 
acid during the progress of an experiment. There is an arrangement 
by which test-quantities of any amount may be taken out without 
causing any loss in measuring the whole current. For this purpose 
a flask is connected air-tight with the pump, and by continuous 
pumping its air is completely replaced by air from the outlet pipe. 
The air pressed out of the flask is not allowed to escape, but is 
passed by means of a caoutchouc tube into the current which goes to 
the gas-meter; of course, in a place where it cannot affect the deter- 
minations of carbonic acid. 
In order that the air-current may take no water from the large gas- 
meter by evaporation, the air before entering the gas-meter first 
passes through an upright cylinder filled with pieces of pumice kept 
moist. 
Where the air issues from this apparatus, there is in the tube a 
psychrometer, in order to measure the temperature and moisture of 
the air which passes into the gas-meter. In the tube which leads to 
the moistening apparatus there is a psychrometer, and several tubes 
for taking out specimens of air, &c. 
The apparatus has been examined since May last in every parti- 
cular, and the author recommends the methods of investigation as in 
every way convenient. It was above all important to prove that the 
carbonic acid disengaged in the saloon could actually be found again 
and determined—a control which has been omitted in all previous 
experiments on respiration. After the author, by numerous experi- 
ments, had investigated all the influences of the apparatus and of 
the methods on the accuracy of the results, he took a stearine candle 
and determined its carbon by elementary analysis. When the suc- 
Phil. Mag. 8. 4. No. 143. Suppl. Vol. 21. 2N 
