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omy. The orbit of this planet is found to be slowly changing its position, its perihelion moving forward by about forty-three seconds per century farther than it ought to move in consequence of the attraction of all the known planets. This deviation was discovered in 1845 by Le Verrier, celebrated as having computed the position of Neptune before it had ever been recognised in the telescope. He attributed it to the attraction of a planet, or group of planets, between Mercury and the sun. His announcement set people to looking for the supposed planet. About 1860, a Dr. Lescarbault, a country physician of France, who possessed a small telescope, thought he had seen this planet passing over the disk of the sun. But it was soon proved that he must have been mistaken. Another more experienced astronomer, who was looking at the sun on the same day, failed to see anything except an ordinary spot. It was probably this which misled the physician-astronomer. Now, for forty years, the sun has been carefully scrutinised and photographed from day to day at several stations without anything of the sort being seen.

Still, it is possible that little planets so minute as to escape detection in passing over the sun's disk may revolve in the region in question. If so, their light would be completely obscured by that of the sky, so that they might not ordinarily be visible. But there is still a chance that, during a total eclipse of the sun, when the light is cut off from the sky, they could be seen. Observers have, from time to time, looked for them during total eclipses. In one instance something of the sort was