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schmidt, of Paris, a jeweller if I mistake not. Three were discovered by Professor James Ferguson at the Washington Observatory. Palisa, of Vienna, made a record for himself in this work. In this country Professors C. H. F. Peters, of Clinton, and James C. Watson, of Ann Arbor, were very successful. The last three observers carried the number above the two hundred mark.

About 1890 the photographic art was found to offer a much easier and more effective means of finding these objects. The astronomer would point his telescope at the sky and photograph the stars with a pretty long exposure, perhaps half an hour, more or less. The stars proper would be taken on the negative as small round dots. But if a planet happened to be among them it would be in motion, and thus its picture would be taken as a short line, and not as a dot. Instead of scanning the heavens the observer had only to scan his photographic plate, a much easier task, because the planet could be recognised at once by its trail.

Recently a dozen or more of these bodies have been found nearly every year. Of course the unknown ones are smaller and more difficult to find as the years elapse. But there is as yet no sign of a limit to the number. Most of those newly discovered are very minute, yet the number seems to increase with their smallness. Even the larger of these bodies are so small that they appear only as star-like points in ordinary telescopes, and their disks are hard to make out even with the most powerful instruments. So far as can be determined,