MICROSCOPIC DRAWING AND ENGRAVING. 
accuracy and fidelity is tlie photographic method. It must, however, 
he 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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