60 PRESIDENTS ADDRESS—SECTION B. 
work, it will be interesting to draw attention to those whose 
discovery involved the use of new methods. 
Of this nature was the discovery early in the century by Davy 
of potassium and sodium by means of electrolysis (1807). Their 
preparation made it possible to isolate several other of the 
elements from their compounds, such as boron, silicon alu- 
minium. 
In 1860 Bunsen and Kirchoff made use of the analysing prism 
for examining the light given off by bodies at a high tempera- 
ture, and perfected the spectroscope as an instrument for 
chemical research. By its means a considerable number of new 
elements have been discovered, notably rubidium and caesium, 
by Bunsen; thallium, by Crookes (1861); indium, gallium, 
scandium, «ec. 
The recent discoveries by Rayleigh and Ramsay of several new 
elements in the atmosphere, and of helium, are of special interest 
and importance, because of the fact that their presence was abso- 
lutely unsuspected, and because of the remarkable way in which 
they were isolated. 
In what has necessarily been a short sketch of the main 
incidents in the historical development of chemical thought, I 
have necessarily omitted mention of many important discoveries 
and many interesting facts and theories. I have, for example, 
scarcely touched upon the enormous field of discovery in the 
application of chemistry to the arts and industries, and not at 
all on its contribution to other sciences, such as physics, 
astronomy, biology, and physiology. I have simply endeavoured 
to present to you in something like their logical sequence those 
prominent features in the development of chemistry which have 
at their time determined tlie direction of research, or been 
specially productive of results. 
The history of chemistry is one of the most fascinating and 
instructive of studies. The discoveries that mark the progress 
of the science contribute alike to the intellectual and to the 
material advancement of humanity, and it is of all the sciences 
the most intimately associated with human progress. 
A new discovery, or the preparation of a new compound, may 
not only be of benefit in increasing our comfort and well-being, 
in developing new industries and improving old ones, but also 
in affording us a clearer insight into the laws that govern the 
material universe, and in aiding us to obtain a more intelligent 
grasp of its meaning. 
