THE STORY OF THE NOVEMBER METEORS. 449 



shower seems first to have fixed the attention of scientific men upon 

 the subject. But he contributed still more to the advance of our 

 knowledge by the success with which he insisted that nearly all such 

 phenomena are periodic, and that therefore there is reason to hope 

 that the causes of them are discoverable. Shortly after, the periodic 

 character of the August meteors was established ; and when the next 

 return of the November meteors to the earth took place, when there 

 was a magnificent display of them exhibited to Europe in 1832, and a 

 still more impressive spectacle seen in America in the following year, 

 the attention of scientific men was thoroughly aroused. 



In England meteors began to be systematically observed, and in 

 this way all that knowledge about them has been acquired which was 

 referred to in the beginning of the lecture. In France the records of 

 antiquity and the annals of distant nations were ransacked ; and by 

 this most useful antiquarian search, no less than ten visits of the No- 

 vember swarm, previous to the shower observed by Humboldt in 1799, 

 have been brought to light. But the first great step toward gaining a 

 knowledge of their orbit was made by Professor H. Newton, of New 

 Haven, in America, who published in 1864 two memoirs, in which he 

 discussed all the accounts that had been collected, extending back to 

 the year a. d. 902. He found, by comparing the dates of the old ob- 

 servations with the modern ones, that the phenomenon is one which 

 recurs three times in a century, or, more exactly, that the middle of the 

 swarm crosses the earth's path at intervals of thirty-three and a quar- 

 ter years. He further showed that meteors which thus visit the earth 

 three times in a century must be moving in one or other of five orbits 

 which he described ; and that therefore, if means could be found for 

 deciding between these five orbits, the problem would be solved. The 

 five possible orbits are the great oval orbit which we now know the 

 meteors actually do traverse every thirty-three and a quarter years ; a 

 nearly circulat orbit, very little larger than the earth's orbit, which 

 they would move round in a few days more than a year ; another 

 similar orbit in which their periodic time would be a few days short 

 of a year ; and two other small oval orbits lying within the earth's 

 orbit. But we owe even more to Professor Newton. He also pointed 

 out how it was possible to ascertain which of these orbits is the true 

 one, although the test he indicated was one so difficult of application 

 that there was at the time little hope that any astronomer would at- 

 tempt it. Fortunately, our own Professor Adams, of Cambridge, was 

 found able to grapple with the difficulties of the problem, and willing 

 to encounter its immense labor, and to him we owe the completion of 

 this great discovery. 



A comparison of the dates of the successive showers which have 



been recorded shows that the point where the path of the meteors 



crosses the earth's orbit is not fixed, but that every time the meteors 



come round they strike the earth's orbit at a point which is twenty- 



TOL. xv. 29 



