MODERN METHODS OF SCIENCE. 587 
any time Newton did assume an hypothesis, it was only for the 
purpose of facilitating his calculations. ‘* Newton’s passage from 
the falling of an apple to the falling of a moon was at the outset a 
leap of the imagination ;” but it was this hypothesis, verified by 
mathematics, which gave to the so-called theory of gravitation its 
present status. 
In regard to light, we are in the habit of connecting with it a 
pure hypothesis ; viz., the impressions of light being produced by 
emission from luminous bodies, or by the undulation of an all- 
pervading attenuated medium; and these hypotheses are to be 
regarded as probable so long as the phenomena of light are 
explained by them, and no longer. The failure to explain one 
single well-observed fact is sufficient to cast doubt upon or subvert 
any pure hypothesis, as has been the case with the emission theory 
of light, and may be the fate of the undulatory theory, which, 
however, up to the present time serves in all cases. 
A theory or scientific speculation, to possess any great weight, 
must receive universal assent by those minds capable of investi- 
gating the subject. Thus the undulatory theory of light is univer- 
Sally accepted as representing the true nature of the operation of 
ight, so far as we are now able to interpret its phenomena. 
Zodlogists equally learned will agree perfectly as regards the 
physical structure of an ape and a man, and thus far their results 
are entitled to universal acceptance ; but some of the same zoolo- 
gists, by the exercise of the imagination and ingenious analogical 
reasoning, deduce the man from the ape, while the others cannot 
See nor recognize any such transformation. In this way both 
Classes present themselves to the curious world, and gather around 
them Supporters ; and, like too many cases in our courts of law, 
the greatest number are convinced not so much by the law or jus- 
tice of the case, as by the ingenuity and special pleading of the 
legal advocates. 
‘At is not my object to criticise the speculations of any one or 
more of the modern scientists who have carried their investiga- 
tions into the world of the imagination; in fact, it could not be 
done in a discourse so limited in time as this, and only intended 
= 88 a prologue to our present meeting. But in order to illustrate 
this subject of method more fully I will refer to Darwin, whose 
name has become synonymous with progressive development and 
oe er a: bere on er daa oP pew A ee Yee ng, F TU gee ee ae go) Wea LS a ee Oe, ee a geo eee ara p= ae 
