THE PRESIDENT’S ADDRESS, 177 
because if we can manage to get at these things, to associate them 
in some way with solar activity, so that there can be no mistake 
about it, then the power of prediction—that power which would 
be the most useful one in meteorology if we could only get at it— 
would be within our grasp.” The writer concludes with this 
practical question, “ What is necessary in order to discover the 
true nature of this nexus? Two things are necessary, and they are 
these. In the first place we must obtain an accurate knowledge of 
the currents of the sun; and secondly we must obtain an accurate 
knowledge of the currents of the earth. The former of these demands 
the united efforts of photography and spectrum analysis; and the 
second of these demands the pursuit of meteorology as a physical 
science, and not as a mere collection of weather statistics. When 
these demands are met by the apt and practical resources which 
are called into play by the pressure of fresh discovery, we shall 
have a science of meteorology placed on a firm and useful basis— 
the Meteorology of the Future.” To make perfect science, how- 
ever (that is, to arrange it in method, and bind its parts together 
with the ligatures of logical sequence), requires the mathematician 
as well as the physicist. It is the glory of our age that even this 
resource is not unlikely to be forthcoming in the right moment. 
Professor Jellett, of Trinity College, Dublin, who presided over 
the Mathematical Section of the British Association at Belfast, in 
his interesting address, referred to the readiness shown by mathe- 
matical analysis to extend its instrumental powers. 
Mathematics exercise already a considerable power over some 
sciences. They rule in Mechanics, Optics, Hydrostatics. Is there 
any probability of their extending their sway into the domains of 
Chemistry or Biology? The question implies another one. How 
far does the method of modern science favour the practice of 
assuming an hypothesis—to be accepted or rejected, according as it 
bears the test of subsequent application to facts? For this is what 
the Mathematician, whose reasoning is essentially deductive, requires. 
Gravitation is an hypothesis which has been completely verified by 
all facts to which it has been as yet applied; and it forms ac- 
cordingly the sure basis of Astronomy. Optics wholly rests on 
hypothesis. The definition of Light—the waves which are assumed 
~ to produce it—the very ether itself which is the material of these 
vibrations, are all hypothetical. But these hypotheses, mathe- 
matically stated, are found to furnish a satisfactory account of 
