140 ANNUAL OF SCIENTIFIC DISCOVERY. 



attention to some peculiar conditions of light, to which he gave the name of 

 fluorescence. M. Nie'pce has made several experiments with substances 

 which possess this peculiar property. A design was traced upon a sheet of 

 white paper with a solution of sulphate of quinine, one of the most fluores- 

 cent bodies; the paper was then exposed to the sun, and subsequently applied 

 to the sensitive paper. The fluorescent parts were reproduced in black, 

 much more intense than that of the paper upon which the design was 

 formed. A plate of glass interposed between the design and the sensitive 

 paper prevented any impression. A plate of glass, colored yellow by the 

 oxide of uranium, produced the same effect. If the design in sulphate of 

 quinine has not been exposed to light, nothing is produced upon the sensitive 

 paper. M. Niepce then tells us that a design traced with phosphorus upon 

 paper, will, without being exposed to light, impress very rapidly the sensitive 

 paper. This impression is, beyond all doubt, due to the formation of phos- 

 phide of silver it is a chemical change quite independent of the luminous 

 effect, and has nothing in common with the other phenomena. He says, 

 however, that the same effects are produced by fluate of lime, rendered 

 phosphorescent by heat. 



Such arc the principal matters to which M. Niepce now directs attention; 

 and if his results are confirmed by further experiments, they must materially 

 change our views of luminous variations. 



Addenda. The details of the method of reproducing engravings by means 

 of the vapor of phosphorus, alluded to above, are given as follows in the 

 Cosmos (Paris) : 



The engraving to be copied is exposed to the vapors of phosphorus burn- 

 ing slowly in the air, the shadows only absorb the vapors ; a sheet of sensi- 

 tive paper prepared with chloride of silver is applied ; after a contact for a 

 quarter of an hour, the engraving is imprinted upon the paper with phos- 

 phuret of silver, which, when strong enough, resists the action of dilute 

 chemical agents. The best mode of operating, consists in placing the 

 engraving in a box in front of a sheet of pasteboard, covering one side of 

 the box, whose surface has been sufficiently rubbed with a stick of phos- 

 phorus. The pasteboard must be rerubbed for each operation; for if the 

 phosphorus is red, it produces no effect. A sheet of water of a centimetre 

 (0 - 4 inch) or more in thickness, does not stop the deposition or action of 

 the vapors of phosphorus. The action is exerted on the sensitive paper 

 even through india-paper; that is to say, that if an engraving on india-papcr 

 is laid upon a sheet of sensitive paper, and these placed together in the box 

 in face of the phosphorescent wall, a negative image of the engraving will 

 be obtained, as if the shadows had behaved like a screen, and the lights had 

 allowed the vapors to pass through and impress the sensitive paper. Only 

 if the exposure be too long prolonged, the shadows will also impress their 

 image, and this will even prevail over the ground. The vapor of sulphur 

 pi-oduces analogous effects, and gives an image or reproduction of the 

 engraving drawn in sulphuret of silver; but this image is not stable. 



LUNAR AND STELLAR PHOTOGRAPHS. 



At a recent meeting of the Royal Astronomical Society, Mr. De la Rue 

 exhibited a great variety of beautiful photographs of the moon and Jupiter, 

 which, through the aid of a magnifying glass of moderate power, exhibited 

 a considerable amount of detail, not visible to the unassisted eye. 



