V04 EEPOET — 1893. 



original source m times reduces the loss, so that it stands at wi times, instead of m' 

 times. 



It remains, and this is more particularly the ohject of the present note, to point 

 out the effect of the telescope upon the angular magnitude and illumination of the 

 bands. If the magnifying power of the telescope exceed the ratio of aperture of 

 ohject glass and pupil, its introduction is prejudicial. And even if the ahove limit 

 be not exceeded, the use of the telescope is without advantage. The relation 

 between the greatest brightness and the apparent magnitude of the bands is the 

 same whether a telescope be used or not, the loss by reflections and absorptions 

 being neglected. The function of the telescope is merely to magnify the linear 

 dimensions of the slit system. 



This magnification is sometimes important, especially when it is desirable to 

 operate separately upon the interfering pencils. But when the ohject is merely to 

 see the bands, the telescope may be abolished without loss. The only difficulty is 

 to construct the very diminutive slit system then required. In the arrangement 

 now exhibited, the slits are very fine lines formed by ruling with a knife upon a 

 silver film supported upon glass. This double slit is mounted at one end of a 

 tube, and at the other is placed a parallel slit. It then suffices to look through 

 the tube at a candle or gas flame in order to see interference bands in a high 

 degree of perfection. 



It is suggested that this simple apparatus could be turned out very cheaply, 

 and that its introduction into the market would tend to popularise acquaintance 

 with interference phenomena. 



6. On the Construction of Specula for Reflecting Telescopes upon 

 New Principles.^ By Dr. A. Shafarik. 



7, Supplementary Note on the Ether. By Dr. Oliver Lodge, F.B.S. 



After my paper on Friday asserting no mechanical stress connection between 

 ether and matter, Mr. Cowper lianyard asked me, 'How, then, does dust polarise 

 light ? ' Or more generally the question might be asked, ' How can ordinary matter 

 affect light in any way ? ' 



The note is suggested by that question, and the point of it is that since the dust 

 is not electrified it cannot (e.v hypotJiesi ) be acted on by oscillating ether, but only 

 by electric oscillations. (The action of dust on the electromagnetic theory has been 

 explained by Lord llayleigh.) Hence all elastic-solid, or mechanical theories of 

 light appear to the author provisionally disproved. 



8. On the Puhlication of Scientific Papier.'!. 

 By A. B. Basset, M.A., F.B.8. 



Two suggestions have been made with regard to the pubhcation of scientific 

 papers — first, that all papers of importance should be published in a central 

 organ ; secondly, that a digest containing an abstract of such papers should from 

 time to time be published. 



I do not think the first scheme could be carried out so as to serve any useful 

 purpose ; for, although it might suit the requirements of a few juvenile societies, 

 it is unlikely that societies of position and standing, which have ample funds at 

 their command for the publication of their proceedings and transactions, would 

 consent to sink their individuality by giving up the publication of papers com- 

 municated to them. Moreover, as many societies derive a considerable portion of 

 their income from the sale of their proceedings, it would be impossible for them to 

 allow the concurrent publication of papers in the central organ, as this might 

 seriously diminish their revenue. 



' Published in full in Industries, 189?. 



