A SILK-SPINNING FISH. 251 



the question of the curative powers of the light transmitted, but regarding 

 the assertion that increased chemical action can be obtained by glazing 

 jDhotographic studios with the cerulean panes. M. Scottelain, the blue glass 

 defender abroad, has fallen into the same errors as his co-believers on this 

 side of the Atlantic: that is, ho confounds the blue-violet rays of the spec- 

 trum with blue-violet transmitted sun-light; while he also reaches the ob- 

 vious absurdity that the violet ray, when isolated from the spectrum, pos- 

 sesses greater capabilities than it had when mingled with the other rays. 

 It is perfectly true that the violet ray is more active, chemically, than the 

 ■other rays; but the latter do not detract from it when combined with it, 

 and the chemical action of white light containing violet rays is precisely 

 as great as that of the violet rays separated and tested alone. Hence it 

 follows, as a matter of course, that a window glazed with white glass trans- 

 mits the whole of the solar rays which reach it, violet among the rest. A 

 window of the same size glazed with violet glass would transmit one-sev- 

 enth part of the rays reaching it, and these would be violet- colored raj^s; 

 but it would not transmit one single violet ray more than the other window. 

 The Photographic Neics adds that, according to Draper and others, all 

 the rays of the spectrum probably possess photogenic power on some sub- 

 stances; and therefore it is but just to M. Scottelari to conceive that he has 

 found that the rays other than violet have an antagonistic influence on 

 that ray, and obstruct its action on bromo-iodide of silver. But Mr. Thos. 

 •Gaflield, of Boston, has recently made some new investigations on this very 

 point, wherein the inferiority of the violet glass to clear glass is most clear- 

 ly shown. Mr. Gaffleld's conclusion relative to the photographic aspect of 

 blue glass accords with our own relative to its employment for curative 

 purposes. He says: "It is undoubtedly true that violet or other colored 

 •screens may be used with advantage in cutting off too much, or in making 

 ■an even diffusion of, light upon the face of the sitter; but it can never be 

 true, while two from six leave a less number than six, that the cutting off 

 of a third, or any fraction, of the chemical rays of sunlight by a violet 

 glass can enable the photographer to obtain more rapid or effective re- 

 sults." — American Chemist. 



A SILK-SPINNING FISH. 



There is a mollusk — the yinna of the Mediterranean — which has the cu- 

 rious power of spinning a viscid silk which is made in Sicily into a textile 

 fabric. The operation of the mollusk is rather like the Avork of a wdre- 

 drawer, the substance being first cast in a mould formed by a sort ef slit in 

 the tongue, and then drawn out as may be required. The mechanism is 

 exceedingly curious. A considerable number of the bivalves possess what 

 is called a hyssus, that is, a bundle of more or less delicate filaments, issuing 

 from the base of the foot, and by means of which the animal fixes itself to 

 foreign bodies. It employs the foot to guide the filaments to the proper 



