PRESIDENTIAL ADDRESS. 127 
are beyond our powers to approach, and, if they are visible, 
that we may not yet see them by first or second hand sight. 
Time will not permit me to follow Lord Rayleigh and 
Professor Ramsay and their collaborateurs throughout their 
memorable searchings for still other constituents of the atmo 
sphere by analyses that were made possible, or at least 
greatly simplified, by operating upon liquid air. 
Each new product had to be submitted to a laborious 
series of examinations, involving the employment of frac- 
tional diffusion, fractional distillation, and other methods 
of-the most rigid physical and chemical scrutiny, aided and 
controlled in part by the use of the spectroscope. Through- 
out this quest, indeed, the spectroscope has proved itself 
quite invaluable as a royal road to identification, and in de 
termining whether or not a simple substance has been 
reached. 
The result of this classical and ever-memorable suite of 
investigations has been the isolation and identification of the 
five new substances—Argon, Helium, Krypton, Neon, and 
Xenon—their addition to the list. of chemical elements and 
to the list of the constituents of normal atmospheric air. 
One of the most notable characteristics of these new gases 
is their disinclination to combination of any kind; but the 
chemist will scarcely rest content until he has tortured them 
into uniom with something. We know how comparatively 
inert nitrogen is, and yet, like all known elements other 
than these, it is known to have its own province of affinity ; 
and we find it entering into combinations of great import- 
ance, highly organised, but leaning to instability. So we 
may yet find it to be with these late additions to the list of 
chemical elements, capable of producing compounds perhaps 
still more complicated in constitution, still more highly 
organised, still more unstable. They may need higher or 
lower temperatures, higher or- lower pressures, or some alto- 
gether new conditions, for their proper affinities to come 
into play. 
OTHER RECENT ANALYSES—COMBUSTIBLE GASES. 
The researches by M. Armand Gautier on the combustible 
gases of the atmosphere are of great interest. His memoir 
also contains some notable modifications of the usual analyti- 
cal methods. He absorbs carbon dioxide by barium hy- 
drate, preferably to caustic potash; the moisture by phos- 
phoric oxide, instead of oil vitriol; and the carbon monoxide 
by iodine pentoxide; the hydrogen, marsh-gas, or other hy- 
dro-carbons, he burns by aspirating through a long tube of 
