MICROSCOPIC DRAWING AND ENGRAVING. 



accuracy and fidelity is the photographic method. It must, however, 

 be observed, that even in this method, as it was practised in the 

 production of the Microscopic Atlas of Messrs. Donne and Foucault, 

 there is still a possible source of inaccuracy remaining, the engraver 

 having to reproduce the photographic picture upon his plate, and 

 for the fidelity of this process, there is no other guarantee than the 

 general accuracy of the engraver's art. 



Measures are, however, now being taken, with a fair prospect of 

 success, by which an optical picture being projected upon a plate, 

 will engrave itself an approach to this has indeed been made ; 

 the photographic picture being projected upon a surface of wood, 

 properly prepared and being there delineated by its own light, as 

 it would be on a daguerreotype plate. The engraver after this has 

 nothing to do but to follow the lines of the picture with his 

 graving tool. 



Attempts, however, are being made to cause the light itself to 

 engrave the plate, and I have seen microscopic pictures of the 

 blood corpuscles thus self engraved, which, if not completely satis- 

 factory as works of art, have been sufficient to impress me with 

 the conviction, that we are not far from the attainment of a 

 measure of such high scientific importance as that of making 

 natural objects engrave themselves. 



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