In the High Heavens - 1910 Author:Robert Stawell Ball Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER III. THE WANDERINGS OF THE NORTH POLE. a visit to Cambridge, Professor E. E. Barnard, the discoverer of the fifth satellite of Jupiter, exhibi... more »ted at the Cavendish Laboratory a most interesting collection of photographs made at the Lick Observatory. These pictures were obtained by a six-inch photographic lens of three-feet focus, attached to an ordinary equatorial, the telescope of which was used as a guider when it was desired to obtain a picture of the stars with a long exposure. Among the advantages of this process may be reckoned the large field that is thereby obtained, many of the plates that he exhibited containing as much as sixteen square degrees. I am, however, not now going to speak of Barnard's marvellous views of the Milky Way, nor of the plate on which a comet wns discovered, nor of the vicissitudes of Holme's comet, nor of that wonderful picture in which Swift's comet actually appears to be producing, by a process of gemmation, an offshoot which is evidently adapted foran independent cometary existence. The picture to which I wish specially to refer in connection with our subject was obtained when the instrument was directed towards the North Celestial Pole. In this particular case the clockwork which is ordinarily employed to keep the stars acting at the same point of the plate was dispensed with. The telescope, in fact, remained fixed while the heavens rotated in obedience to the diurnal motion. Under these circumstances each star, as minute after minute passed by, produced an image on a different part of the plate; the consequence of which was that, when the picture was developed, the record which the star was found to have left was a long trail instead of a sharply defined point. As each star appeared to describe a circle in the sky aroun...« less