'chemical sciexce. 193 



him in a vision by the chief of the genii of the elements. He there 

 recounts how the attendant genii had sought to fix the fleeting 

 images which were seen reflected in placid water, or painted on the 

 retina of the eye ; and, after some details, he describes how they at 

 last succeeded in discovering a subtle adhesive liquid quickly drying, 

 and capable, when poured on a flat surface, of fixing thereon, per- 

 manent!}', and in the twinkling of an eye, the images of whatever 

 natural scene was presented before it. Awaking from his vision, 

 Tiphaigne propounds three problems which had been suggested to 

 him by the genii, for the sagacity of mundane philosophers to un- 

 ravel : the nature of the glutinous liquid, the method of preparation 

 and best means of employing it, and the rationale of the action which 

 was exercised upon it by light. The account given by the genii (the 

 writer states) is almost, to its minute details, the present system of 

 collodion photography ; whilst Tiphai^ne^s three problems, important 

 as they have since become, are still very far from a satisfactory 

 settlement. 



This is a very ingenious identification of a past speculation with 

 present fulfilment of which the amusing writer in the London 

 Review says : — " Never before, in modern ages, have we known so 

 clear an instance of a prophecy and its fulfilment." We cannot 

 agree with the writer to the full extent : he does not quote the words 

 of the author, which, in literary evidence, it is very important should 

 be done. That any one should wish for the fixing of a pleasing 

 image, in a mirror, or in water, the first natural mirror, is reasonable 

 enough, and far beyond the fantasies of a century since ; but the 

 how is a matter not so easily traceable. The Editor of the Year-Booh 

 of Fads proposed rolling over a printer's form of type, instead 

 of beating with balls, long before the composition inking-rollers 

 were invented. The discovery of the process of making the com- 

 position for the rollers was the great secret, without wliich this im- 

 portant portion of printing machinery would, in all probability, 

 never have been perfected, We are too apt, in seeking the history 

 of discovery, to reason a posteriori. This tracing of collodion photo- 

 graphy reminds us of the story of the magnetic correspondence in 

 the Spectator, which has been regarded as the foreshadowing of 

 electro-telegraphy. 



THK USES OF PHOTOGRAPHY. 



Under. this comprehensive title, the writer of an able paper in the 

 Mechanics' Magazine has grouped the more striking results obtained 

 by photographic agency, which far exceed even the sanguine antici- 

 pations of some oue-and-twenty years since — the date of the birth of 

 this wonderful art. 



A Photographic Recording Apparatus has been adopted for regis- 

 tering the meteorological indications of the instruments at the Royal 

 Observatory, Greenwich, with the greatest advantage. Since its 

 introduction, the staff of observers has been reduced in number, and 

 the fatiguing process of nocturnal observation has been altogether ' 

 superseded. The following is a description of the general principles 



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