470 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1906. 



bodies from the most distant regions to which our 

 telescopes can [jenetrate. Up to this distance, we see 

 the stars just as they are."" The companions of some 

 of the Algol variables are usually spoken of as " dark 

 bodies," but I have shown elsewhere that we have no 

 reason to think that they are really dark. The com- 

 panion of .'\lgol, for example, may be a star of the 5th 

 magnitude — a comparatively bright star — and yet be 

 cjuite invisible to us, as neither the telescope nor 

 spectroscope would show any trace of its existence. 

 The little evidence we have tends to show ttiat the 

 satellite of Algol is tiol a dark body. The idea of " dark 

 bodies " and " dark stars " seems to have been based 

 on the existence of this eclipsing satellite; but it has 

 been recently found that a difference of brightness of 

 two magnitudes between the components of a spectro- 

 scopic binary star — like Algol — would be quite sufficient 

 to obliterate the spectrum of the fainter star, the 

 spectroscope merely showing the spectrum of the 

 brighter component. Dark bodies may exist in space, 

 and probably do, but as yet vie have no positive evi- 

 dence of their existence. The " holes in the Heavens " 

 are, I think, real, and "dark companions" of Algol 

 variables have probably no existence except in the 

 imagination of some astronomical writers. 



It has been stated by several writers that the exis- 

 tence of these " holes " indicates that the Milky Way 

 has a small extension in the line of sight; or, in other 

 words, that it forms a comparatively thin stratum of 

 stars. But Professor Seeliger has shown that, accord- 

 ing to the Law of Probabilities, if the number of stars 

 be the same in both cases, the probabilitv against the 

 occurrence of these holes is just the same whether the 

 extension of the Milky \\'ay in the line of sight be great 

 or small.! ^^'e cannot, therefore, come to anv con- 

 clusion as to the actual thickness of the Milkv Way 

 from the appearance of these dark spots. It mav have 

 a great extension in the line of sight, or it may be com- 

 paratively thin in that direction. The cause of these 

 " holes " must probably be looked for in the influence 

 of some "clustering power," as Sir William Herschel 

 termed it, which tends to draw the stars away from 

 certain spots and accumulate them in others. The 

 existence of globular and other clusters close to dark 

 and comparatively starless spots seems very sugges- 

 tive in this connection. If these dark spots were due 

 to intervening dark bodies, there seems to be no reason 

 why we should find them so often close to rich regions. 



* Harper's Magazine, October, 1904. 



t A strophysical Journal, Vol. 12, page 377. 



Cels and Electric Light. 



It appears tolerably certain that some species of eels migrate 

 into the sea to spawn, and that the spawn hatches in the sea 

 while the young undergo their transformations near sea 

 shores. A belief, which is more doubtful of proof, is that 

 the conger-eel does a good deal of damage to the coast 

 fishing industry, and that this animal has so great a dislike 

 to light that it will not migrate to the open sea when the 

 moon is at the full. .\n experiment which will resolve 

 some of these doubtful questions is to be made under the 

 auspices of the Biological Society of Copenhagen. In the 

 strait known as the " Little Belt," electric larnps are to be 

 fi.xed at the bottom of the channel in order to deter the 

 congers from making their way out to the open sea. The 

 result of the experiment will be watched with much atten- 

 tion, both as regards the distribution of the congers and the 

 pifect on the shoals of food fishes. 



Royal Society, 



Ladies* Conversazione. 



The second soiree of the Royal Society, that to which 

 it is customary to in\ ite ladies, was held at Burlington 

 House towards the end of last month, and attracted a 

 large and representative gathering. Some of the ex- 

 hibits shown in May were repeated, but notwithstand- 

 ing this there was a goodly number of fresh ones 

 possessing intrinsic interest of which mention may be 

 made here. 



Voice figure — landscape pattern. 



The pretty series of voice figures exhibited by Mis. 

 Watts-Hughes, with the able co-operation of Mr. 

 Richard Kerr, F.R.A.S., were of singular interest. 

 They were entirely produced by the vibrations of notes 

 sung into a tube communicating with a cup-shaped 



-con\oIuted pattt^rn. 



vessel, a piece of india-rubber being tightly stretched 

 over the top of the vessel; on this latter there rested a 

 piece of paper covered with moist water-colour. As 

 the sound waves impinged upon the under-side of the 

 membrane a variety of devices arranged themselves 



