DAGUERROTYPE. 



iety of London, and lastly to the chair of com- 

 para'tive physiology at the Jardin des Plantes. He 

 was also a contributor to several scientific jour- 



nals, and the principal labourer in the Listoire des 

 Mammiferes, published in conjunction with M. 

 Geoffrey St Hilaire. His death took place in 1838. 



D 



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DAGUERROTYPE, the name applied to a re- 

 cent invention of M. Daguerre of Paris, by which 

 he fixes upon a metallic plate the lights and 

 shadows of a landscape or figure solely by the ac- 

 tion of the solar light. The interest excited in 

 this invention has been increased by the publication 

 of a series of experiments made by our coun- 

 tryman Mr Talbot, directed towards the same ob- 

 ject, and producing nearly similar results. So far 

 back as the year 1800, the attention of Sir Hum- 

 phrey Davy and Mr Wedgwood was directed to 

 the subject by the extraordinary eflfect produced by 

 light upon the nitrate of silver, which led them to 

 hope that the purposes of the artist might be as- 

 sisted by the susceptibility of the metallic oxide. 

 The first experiment was made by Mr Wedgwood 

 for the purpose of copying paintings upon glass, 

 and was eminently successful ; the copy obtained 

 possessing all the figures of the original, in their 

 native shades and colours: it was also in a high 

 degree permanent, so long as it was preserved from 

 the action of the light. The same gentleman dis- 

 covered that the shadow of an opaque object 

 thrown upon the paper was copied in outline with 

 great correctness ; but though both these celebrated 

 chemists were constant and persevering in their 

 endeavours to render the drawing permanent, they 

 were entirely unsuccessful ; the lighter shades 

 darkening by exposure and thus obliterating the 

 impression. Their failure in this important object 

 was published with their experiments in the philo- 

 sophical transactions, and both having given up the 

 attempt, their discoveries have since remained 

 unimproved. But in the meanwhile M. Daguerre, 

 it appears, struck by some hints he had received 

 from a friend, has steadily pursued his experiments 

 for the last twenty years, and having at length at- 

 tained his object, has declared his discoveries, and 

 claimed the invention as his own. 



A polished metallic plate is the substance made 

 ase of, and being placed within the apparatus is in a 

 few minutes removed and finished by a slight me- 

 chanical operation. The sketch thus produced is 

 in appearance something similar to aquatint, but 

 greatly superior in delicacy ; and such is the ex- 

 traordinary precision of the detail that the most 

 powerful microscope serves but to display the per- 

 fection of the copy. The first efforts of the in- 

 ventor were directed towards architectural subjects, 

 and a view of the Louvre and Notre Dame are 

 among the most admired of these engravings. In 

 foliage he is less successful, the constant motion in 

 the leaves rendering his landscape confused and un- 

 meaning -. and the same objection necessarily ap- 

 plies to all moving objects, which can never be pro- 

 perly delineated without the aid of memory. But 

 in the execution of any stationary subject, build- 



ings, statues, or the bodies of animals, the fac- 

 simile is perfect; and the value of the invention 

 may therefore be easily conceived. 



Several eminent artists have examined the de- 

 signs, and were equally delighted with the precision 

 and delicacy of the representation. Among the 

 sketches exhibited by the projector was a marble 

 has relief and a plaster imitation ; the first glance 

 was sufficient to detect the difference between 

 these two; and in three views of a monument 

 taken in the morning, noon, and evening, the spec- 

 tators easily distinguished the hours at which they 

 were executed, by the difference of the light, 

 though in the first and last instances, the sun was 

 at an equal altitude. But perhaps the anatomist 

 or zoologist will derive the greatest advantages 

 from the discovery, the form of the animal being 

 as easily studied from the drawing as from the ori- 

 ginal, and the most powerful microscopes not hav- 

 ing hitherto detected the smallest deficiency in the 

 details. Nor is the invention devoid of interest to 

 the astronomer, for the light of the moon is suffi- 

 cient to produce the usual results, requiring only 

 additional time for its operations. The following 

 extract from " Le Commerce " is sufficient to sub- 

 stantiate its value in this respect: " The experi- 

 ments on the light of Sirius have confirmed the 

 testimony of natural philosophy, and abundantly 

 proved that the stars are bodies of the same nature 

 as the sun ; at the request of M. Biot, M. Daguerre 

 has submitted his apparatus to the influence of the 

 light of the moon, and has succeeded in fixing the 

 image of that luminary. We observed that the 

 image had a trail of light something like the tail 

 of a comet, and we ascribed it to the movement of 

 the body during the operation, which is of much 

 longer duration than that by the light of the sun.'" 



In the spring of 1834 Mr Talbot began a series 

 of experiments, with the hope of turning to useful 

 account the singular susceptibility evinced by the 

 nitrate of silver when exposed to the rays of a 

 powerful light; but not being acquainted with the 

 researches of former chemists on the subject, he 

 commenced with the same disadvantages which had 

 baffled the skill and perseverance of Sir Humphrey 

 Davy. The plan he at first proposed was, to re- 

 ceive a well-defined shadow upon a sheet of paper 

 covered with a solution of nitrate of silver, by 

 which means the part shaded would remain white, 

 while the surrounding portion was blackened by 

 exposure to the light. But he was well aware 

 that the sketch thus obtained would require to be 

 protected from the rays of the sun, and examined 

 only by an artificial light. He had carried these 

 inquiries to some extent, and became possessed of 

 several curious results before he learnt the steps 

 which others had taken to attain the same object' 



