202 JOURNAL OF THE PLYMOUTH INSTITUTION, 
The publication of Newton’s Principia in 1687 laid foundations 
of scientific thought that have never been disturbed. To quote 
Professor Draper: ‘On the principle that all bodies attract each 
other with forces directly as their masses, and inversely as the 
squares of their distances, Newton showed that all the movements 
of the celestial bodies may be accounted for, and that Kepler’s 
laws might all have been predicted—the elliptic motions, the 
prescribed areas, the revelations of the times and distances.” As 
we have seen, Newton’s contemporaries had perceived how circular 
motions could be explained. That was a special case ; but Newton 
furnished the solution of the general problem, containing all 
special cases of motion in circles, ellipses, parabolas, hyperbolas— 
that is, in all the conic sections. 
The Alexandrian mathematicians had shown that the Aleeetioe 
of movement of falling bodies is toward the centre of the earth. 
Newton proved that this must be the case, the general effect of 
the attraction of all the particles of a sphere being the same as if 
they were all concentrated in its centre. 
Newton’s merit consisted in this, that he applied the laws of 
dynamics to the movements of the celestial bodies, and insisted 
that scientific theories must be substantiated by the agreement of 
observations with calculations. 
Man ceased to be the centre of all things except to himself. 
Each one became an infinitesimal speck; the earth on which he 
lives only a slightly larger one, and only one of the incalculably 
-numerous components of the universe. 
The interest of Science, still greatly centered in the relation of 
our earth to other worlds, until the advent of the Herschels’ 
mathematics applied to the stars, now became exact. Double 
suns are discovered, nebule found out, and for the first time men 
believed that there were other suns than ours, The further 
problem of worlds fitted for habitation must be left to our own 
times. 
One of the principal retardations of Science hitherto had been 
the theory of the emanation of light, instead of the ethereal undula- 
tory wave theory. This was now broken down, and vast strides 
in scientific thought immediately resulted. 
To give an idea to what a pitch accuracy of thought had 
arrived at this time, let me say that Romer fixed the passage of 
