372 Notices respecting New Books. 



by the eye. Now we have evidence from actual measurement that 

 the stars a and j3 Centauriand 61 Cygni, with our sun, are certainly 

 the only stars within a sphere of something like 120 billions of 

 miles in diameter. Ought not the stars composing a stream to be 

 sufficiently near each other to afford some degree of similarity of 

 parallax ? We can easily understand that a group similar to the 

 Pleiades may be physically connected. From double-star measure- 

 ments we are certain of the physical connexion of a large number 

 of pairs, and also of many triple combinations, without calling in 

 the aid of the theory of probabilities to "absolutely demonstrate" 

 such a connexion ; and from the certainty thus afforded by mea- 

 surements we may pass on by analogy to infer that the larger star- 

 clusters, as for example the Pleiades, are also physically connected. 

 When, however, we extend this analogy to " star-streams," the 

 first point that strikes our attention is the great distances at which 

 the component stars of the stream must be from each other. Any 

 two stars situated on the connecting band of Pisces (one of Mr. 

 Proctor's illustrations) at an angular distance of 1 degree would, 

 with a parallax equal to that of 61 Cygni, be more than a billion of 

 miles apart ; and as we are ignorant of their parallax, they may, 

 for aught we know, be much further asunder. Consequently each 

 portion of the double star-stream of Pisces, if it have a real exist- 

 ence, must be very long; in fact, if the stars be not optically near 

 each other, they must be at pretty nearly equal distances from our 

 sun, and would, of course, present nearly similar parallaxes. 



We have been particularly struck with the constant appeal by 

 Mr. Proctor, on the one hand, to the application of the theory of 

 probabilities to substantiate his views, and, on the other, the reite- 

 rated improbability that the present arrangement of the components 

 of the starry heavens is a chance arrangement. As regards the 

 latter, we cannot for a moment conceive of an astronomer holding 

 such a view. Upon reading Mr. Proctor's argument against chance 

 distribution, and examining his illustrations from Argelander and 

 Chacornac on pp. 30, 31, 33, and 34, we took in the palm of our 

 hand a pinch of fine sand (the silver sand of commerce) ; and having 

 got rid of the superfluous grains by depositing them in the other 

 palm, so as to leave on the hand a mere dust of sand, we sprinkled 

 this dust lightly on a black japanned tea-tray. Having done this 

 a few times we obtained a fine collection of clustered grains, a mi- 

 niature cluster in Perseus for example, and specimens as fine as any 

 engraved by Mr. Proctor, of star-streams and star-sprays, which 

 were finely seen by the aid of an ordinary reading-lens. Now the 

 mode of production of these clusters, streams, and sprays of sand 

 would by most persons be attributed to " chance ;" but such is not 

 the case, as shown by Mr. Proctor on p. 100. It was altogether 

 out of our power to produce any specified form on the tray ; yet we 

 cannot doubt the presence of " forces " so operating as to give to 

 each grain of sand the exact position it occupied on the tray. 

 Every feature insisted on by Mr. Proctor was there ; the very vacant 

 spaces which he considers so significant were seen ; and although 



