134 PROCEEDINGS OF SECTION B. 
ments should be repeated, old experimental ground traversed 
again, using the new tools and appliances with which modern 
science keeps supplying us; it may be mstruments of greater 
precision; it may be a new method of research, such as 
spectral analysis, or photography, or the X-ray ; it may be an 
improved or novel method of exact chemical analysis; or 
new devices for producing extremes of heat or cold; it may 
be liquid air and a helium thermometer; or the discovery 
of a new principle, or new substances; or something else 
that will exalt our powers of research. This apples, of 
course, to every department of science, but I am regarding 
it especially in connection with atmospheric air. There 
is great room for the repetition and extension of old experi- 
ments, and the devising of new ones. Is not the long neglect 
of Cavendish’s “ residue ’’ still fresh in our minds? 
Systematic and periodic analyses are needed all over the 
world in connection with the air and rain—chemical climat- 
ology. The analyses ought to be made with the utmost | 
exactness by recognised standard methods, which ought 
always to be stated. The recent discoveries of Rayleigh and 
Ramsay have rendered it necessary for us to overhaul all our 
old results, and follow by rigid analyses the changes m the 
composition of the air throughout the air-traffic in rock and 
soil and river and sea referred to above. 
The changes in the air brought about by the vegetable 
and animal worlds have only been very crudely stated. 
The exhalations of the animal and the plant, their out- 
ward breaths. require to be submitted to the same rigid and 
exhaustive examination as that to which the atmosphere is 
now being subjected by the chemist and spectroscopist ; and 
it may be that equally startling discoveries in both these 
directions are awaiting the patient investigator. Besides 
these, we have the great reservoir of the atmosphere itself to 
further explore throughout its depths. 
Finally, the study of the chemistry of the atmosphere has 
led us to the study of other atmospheres than ours—a study 
that is teaching us much concerning the atmosphere of the 
earth. We read our own history in nebule, and stars, and 
sun, and planets. This has been made possible through the 
application of especially two most wonderful instruments of 
research—spectral analysis and photography. The examina- 
tion, and ultimately the explanation, of the presence of 
certain dark lines in the solar snectrom brovght us by one 
bound to a solar chemistry, and then, as a corollary, to a 
chemistry of the stars. We thereby recognised in the sun’s 
atmosphere certain chemical elements known to exist on 
