The Legacy Of Research
left by Newton may truly be called "immense." And Herschel does well to modify his statement as to the "triumph," and postpone it yet another century.
For it must be borne in mind that no astronomical system is a strictly verifiable fact. The circulation of the blood is a verifiable fact, and it has been verified. No announcement of the discovery of a new demonstration of its truth could now attract any attention on account of its merits as proof.
Not so as to the earth's motion. The proofs of that have always been merely referential and cumulative. The final, the crowning point of demonstration has never been made, and probably never can be reached. Who can say that he ever saw the earth move? Hence it is that every successive item of cumulative evidence is hailed with pleasure and excitement. Thus was it with Torricelli's, Newton's, Richer's, Roemer's, and Bradley's discoveries; thus with all the brilliant inventions in mechanics by means of which the illustration and explanations of these discoveries became possible—explanations which, after all, not one man in a thousand can understand.
Post-Galilean Astronomy.
A few words in addition to what we have already said concerning the great discoveries made since Galileo's time, and we close.
Three of these discoveries, without which the Copernican theory as to demonstration would be but little better off than the Ptolemaic, merit special mention. They are:
First. The Newtonian theory of gravitation.
Second. The discovery of the shortened pendulum, showing the diurnal motion of the earth.
Third. The velocity and aberration of light, showing the annual motion.
It is scarcely necessary to enter into any detail concerning the so generally known, great, and universal principle of gravitation.
The Shortened Pendulum.