Thus confirmed by Bradley, Roemer's progressive transmission of light became an incontestable fact.
Then followed the experiments projected by Arago to determine the velocity of light, (1838,) which for eleven years remained a merely ingenious suggestion, until realized by MM. Foucault and Fizeau.
From 1840 to 1842, Struve, in Russia, made numerous observations to obtain the exact value of aberration.
In 1856, the Institute of France awarded to M. Fizeau, for his successful demonstration of Arago's suggestion, the triennial prize of thirty thousand francs founded by the emperor, "for the work, or the discovery, which, in the opinion of the five academies of the institute, has done most honor and service to the country."
Finally, in 1862, M. Foucault, perfecting his apparatus, measured the velocity of light by an admirable experiment in physics, which renders not only sensible, but even measurable, the time employed by light to run over a path of twenty metres, (65 feet 7.4 inches,) although this time barely equals 1/15000000 of a second!
And yet, after all this, there still remains a doubt as to positive certainty of accuracy in the calculations.
The sun's parallax, calculated from observations of the last transit of Venus over the disk of the sun in 1769, is fixed at 8.58 seconds, and on this basis is ascertained the distance from the earth to the sun.
For reasons too long to detail here, many distinguished astronomers are not entirely satisfied with the determination of 8.58 seconds, and prefer to wait for the next transit of Venus, in 1874, for a full and satisfactory solution of all doubts on the subject!
Conclusion And A Proposition.
Thus, after a lapse of two hundred and thirty-five years, filled with unremitting labor and triumphant results in the field of astronomical discovery, it appears from the showing of those most competent to judge that something yet remains to be produced in the way of demonstration of the astronomical system as now accepted.