September 23, 1898.] 



SCIENCE. 



393 



into a smaller space, which would produce 

 an intensification of its action. It is pos- 

 sible, also, that the photographic plate may 

 be relatively more active with a bright image 

 than with a faint one, which would give an 

 advantage to the small relatively bright 

 image of the portrait lens. This idea seems 

 to be partly borne out by some experiments 

 with a small lantern lens. This lens, 

 1^ inches in diameter and about 5^ inches 

 focus, is much quicker than its light ratio 

 would warrant, for it will photograph in a 

 few minutes what the ordinary quick-acting 

 portrait lens would require several hours to 

 show. This was strikingly shown in photo- 

 graphs taken with it of the Milky Waj\ 

 The scale of this lens is very small, and the 

 cloud forms are so compressed that they 

 act as a surface, and not as an aggregation 

 of individual stars, as they must do in a 

 larger telescope. If the focus is increased, 

 the stars are scattered and the cloud no 

 longer acts as a surface. With this small 

 lens the earth- lit portion of the new moon 

 was readily photographed in a single second, 

 while with a 6-inch portrait lens of ratio ^- 

 from 20 to 30 seconds were required to 

 show it well. The brighter cloud forms of 

 the Milky Way were shown in from 10 to 

 15 minutes' time, while with the larger 

 lens upward of thi-ee hours were required. 

 Some of the diffused nebulosities of the 

 Milky Way, notably in the region of 

 Antares, are shown more quickly and more 

 satisfactorily with this small lens, and a 

 great wing-like nebula involving the star 

 Nu Scorpio was discovered with it. 



A list of discoveries made with these 

 small lenses would be tedious; one of the 

 most interesting, however, cannot be passed 

 over because of its importance. There is 

 no object in the entire heavens better known 

 than the great nebula of Orion. With the 

 lantern lens, a great curved stream of nebu- 

 losity was shown on the plates of this region 

 covering a large portion of the constellation 



and some 17° long. It was found later 

 that this had already been discovered by 

 Professor Wm. H. Pickering with a 2-J-inch 

 lens in 1889. This object seems to be an 

 outlying appendage of the great nebula. 

 The discovery very much extends our 

 knowledge of the complicated and far- 

 reaching influence of this mysterious ob- 

 ject. In several other cases the photo- 

 graphic plate has shown us that the nebulse 

 are far vaster than we had ever conceived 

 them to be, for their fainter extensions are 

 not seen by the eye. What this knowledge 

 may ultimately lead to in the reconstruc- 

 tion of our ideas of space and its contents 

 can hardly be anticipated just now, though 

 it must, necessarily, very greatly influence 

 those ideas. 



We have spoken of the Pleiades and the 

 entangling nebulosities shown by photog- 

 raphy to involve the stars of the cluster. 

 The portrait lens has shown us that not 

 only are the individual stars of this group 

 involved in a nebulous system, but that 

 streams and masses of this filmy matter 

 stretch out for great distances all about the 

 cluster. 



The photographic plate has shown itself 

 especially adapted, when used with the 

 rapid portrait lens, for the accurate register- 

 ing of the paths of meteors, and it promises 

 to be of special value during the expected 

 return of the November meteors this year, 

 when a more exact determination of the 

 radiant will be obtained from the photo- 

 graphs, and hence the orbit of the meteor 

 stream will be better known. 



In the reduction of the measures of the 

 photographic plates for the great Cape 

 Photographic Durchmusterung, Kapteyn 

 discovered another ' runaway ' star with a 

 proper motion of 8.71 seconds a year, 

 which is much greater than that of the cele- 

 brated 1830 Groombridge, and is at present 

 the largest proper motion of any known star. 



There are very few departments of as- 



