2º. The eclipse happened at nine o'clock, says the astronomer.
3º. The eclipse happened at the time deducible from the tables constructed according to Newton's law, says he again.
4º. That results from the earth's turning around the sun, says Galileo finally.
Where then is the boundary between the fact in the rough and the scientific fact? To read M. LeRoy one would believe that it is between the first and the second stage, but who does not see that there is a greater distance from the second to the third, and still more from the third to the fourth.
Allow me to cite two examples which perhaps will enlighten us a little.
I observe the deviation of a galvanometer by the aid of a movable mirror which projects a luminous image or spot on a divided scale. The crude fact is this: I see the spot displace itself on the scale, and the scientific fact is this: a current passes in the circuit.
Or again: when I make an experiment I should subject the result to certain corrections, because I know I must have made errors. These errors are of two kinds, some are accidental and these I shall correct by taking the mean; the others are systematic and I shall be able to correct those only by a thorough study of their causes. The first result obtained is then the fact in the rough, while the scientific fact is the final result after the finished corrections.
Reflecting on this latter example, we are led to subdivide our second stage, and in place of saying:
2. The eclipse happened at nine o'clock, we shall say: