286 Chemical Analysis of the Atmosphere. 
of the volume of air to that of dry air, or rather to the degree of 
humidity shown by the experiment, appears to me too minute to 
have any sensible influence on the very feeble proportion of carbonic 
acid existing in the air. . ry 
To determine the limits of the proportion of carbonic acid appre- 
ciable by this method, I operated upon air taken from two feet abc 
a small charcoal fire, and passed it through barytic water, after it had 
passed through the lime tube. Although the carbonic acid was 
to be near one per cent. in the volume of air, the barytic water 
was not troubled. When I repeated it with a similar air, but more 
highly charged, viz. two per cent. of carbonic acid, the barytic water 
was decidedly affected. But this proportion of carbonic acid sur- 
passes, by more than thirty times, the maximum found by de Saus- 
sure in the atmosphere. I would observe, that in the latter experi- 
ments, I let the water flow in a natural stream. By slackening the 
current, or by lengthening the lime tube, we might probably operate 
upon air more highly charged with carbonic acid. 2 
To be certain that the current of air does not bring with it any 
sensible quantity of water, I placed a second hygrometric tube be- 
tween the lime tube and the vessel A. In several experiments 
this kind, I never observed the least increase of weight in this tube. 
In a series of experiments undertaken with a view of studying my 
apparatus, I constantly obtained results included within the limits of 
those obtained by de Saussure. . 
It appears therefore that the method now described furnishes an 
easy and certain means for ascertaining the proportion of the two ac- 
eidental principles of the atmosphere. I think it susceptible of being 
extended to those researches which are properly styled eudiomet- 
ric.* Perhaps a method may be derived from it, more exact than 
those now practised to determine the proportion of the oxygen, which 
has hitherto been scarcely brought within one hundreth of the point 
of rigorous exactness. It would also be desirable to employ some an 
ogous methods in researches into the other elements which the veal 
mosphere appears to contain. For this purpose currents of air should 
be passed, for some time, through different reagents, which might be 
_ enclosed either in tubes similar to those above described, or through 
Wolf's bottles, and in order to act upon large masses of air, an app? 
te Is it not to be regretted that the term eudiometry and eudiometer should wes 
plied exclusively to the art of determining the quantity of oxygen in the ind more 
i ts for that purpose ? Would not the terms oximetry and oximeter be more 
iate 2—Tr. , 
