ence has advanced only by the labors of philosophers, who pursued it as a matter of taste and not officially. Was it not as an amateur that the canon Copernicus discovered the true system of the world? As an amateur on his little estate at Woolstrop the thinker Newton discovered universal gravitation. Cavendish, who first weighed the earth, was an amateur. Belonging to a noble and wealthy English family, he devoted his whole life to the advancement of science. He was, said Biot, the wealthiest of the learned, and probably also the most learned of the rich.
Are those not also amateurs who have made the most advance in the study of the moon? Hevelius, a counselor of Dantsic, who first undertook to define the form and position of the lunar spots? To whom do we owe the details of lunar topography? To enthusiastic amateurs in astronomy—Schroeter and Lohrman in Germany, and the machinist Nasmyth in England. And now we can count by the hundred the men who give their time to observing our satellite in all its details; and a new fact is added every day to those which we already know.
The knowledge which we possess of the spots and faculæ of the sun is also derived from materials collected by amateur astronomers. We cite first Fabricius, who, living at the beginning of the seventeenth century, first observed the spots and ascertained the period of solar rotation. An amateur, also, Schwabe, of Dessau, discovered the periodicity of the solar spots, and Carrington, Warren, and De la Rue made their admirable studies on the central star of our system. Janssen found a way to observe the protuberances without being obliged to wait for the rare and brief instants of total eclipses; the musician, William Herschel, extended the frontiers of the solar republic, and radically transformed sidereal astronomy; the mathematician, Le Verrier, then a stranger to the Observatory of Paris, discovered Neptune in the depths of space, a milliard of leagues from here; and Dambouski, Burnham, and Gledhill, skilled observers of double stars, have measured the couples that move in remote parts of the sky.
We could not, if we should try, cite the names of all the amateurs who have discovered comets. It was an amateur in astronomy, Flangergues, of Viviers, who first observed the celebrated comet of 1811, the length and brightness of whose tail were the wonder of our ancestors. At seventy-one years of age this indefatigable amateur of astronomical science was so happy as to discover a second comet. Among comet-hunters, we should not forget Pons, porter of the Observatory of Marseilles, who had in France no rival as a discoverer of comets except Mersier, Director of the Observatory of Paris, whom Louis XV surnamed the "comet ferret."
Besides their activity as discoverers, amateurs have also done
