MICROSCOPIC DRAWING AND ENGRAVING. 



lines composing a band, which a power of 2000 would barely 

 render visible to average eyes. Assuming that such eyes could 

 see distinctly without microscopic aid the lines of a band consisting 

 of 150 to an inch, it is evident that a power of 2000 would render 

 equally visible those of a band, the lines of which would be 300000 

 to an inch. I am not aware that Mr. Nobert, or, any other artist, 

 has ever produced such lines, and consequently doubt the existence 

 of any such artificial test for a power of 2000. 



31. I now come to notice a sort of microscopic engraving, which, 

 though it is at once the most curious and difficult, has not, so far 

 as I am informed, had as yet any directly useful application. 

 Regarded, however, as an example of mechanical ingenuity and 

 skill, and as an artistic tour de force of the highest order, it is 

 full of interest. 



However much we may admire the production of the micrometric 

 scales and microscopic test-plates described above, there is nothing 

 in them to excite surprise, save the precision which is combined 

 with such extreme minuteness. To draw a series of parallel lines 

 of regulated length and uniform intervals, is a problem, to the 

 solution of which it is easy to conceive that finely constructed 

 mechanism can be adapted ; but when it is proposed to delineate 

 objects and characters, in which no such regularity prevails, and, in 

 tracing which, the point of the graving tool must pursue a course 

 determined by conditions, which obviously cannot be represented 

 by any kind of mechanism, and to accom- 

 plish which it must be guided, directly or 

 indirectly, by the hand, a problem of quite 

 another, and far more difficult order, is 

 presented: such, however, is the curious 

 and complicated problem for which Mr. 

 Froment, already named, has found . a 

 solution. 



This eminent artist has succeeded in 

 producing manuscripts and drawings, en- 

 graved upon glass, on a scale of minuteness 

 in no degree less surprising, though far 

 more difficult of execution than the test- 

 plates of Mr. Nobert. 



To enable the reader more easily to 

 appreciate these wonderful productions, we 

 have given in fig. 25 the forms and magni- 

 tudes of five small circular spaces, A, B, c, D, 

 E, the diameters of which are severally the 6th, 12th, 30th, 70th, 

 and 160th of an inch. 



Mr. Froment wrote for me, in less than five minutes, within a 



