FROMENT S MICROSCOPIC WRITING. 



circle of glass, the 40th. of an inch in diameter, less, therefore, by 

 one third than the small white spot c, fig. 26 ; the sentence which, 

 when magnified in its linear, 120, and in its superficial dimen- 

 sions, 14400 times, presented the appearance shown in fig. 26. 



Fig. 26. 



On the occasion of the Great Exhibition in 1851, the characters 

 and figures shown in fig. 27 were engraved by Mr. Froment, 

 within a circular space equal to that shown at c in fig. 25. 



32. As the method by which these marvellous effects are pro- 

 duced is not yet patented or made public, we are not at liberty to 

 explain its details ; but it may be stated generally to consist of a 

 mechanism by which the point of the graver or style is guided by 

 a system of levers, which are capable of imparting to it three 

 motions in right lines which are reciprocally perpendicular, two 

 of them being parallel, and the third at right angles to the surface 

 on which the characters or design are written or engraved. The 

 combination of the motions in the direction of the axis parallel 

 to the surface on which the characters are engraved or written, 



73 



