MICROSCOPIC DRAWING AND ENGRAVING. 
exact aliquot part of a standard unit of length, has, nevertheless, 
produced hands engraved by a diamond point on slips of glass, 
consisting of a greater or less number of parallel lines, separated 
by intervals of surprising minuteness. 
Some remarkable specimens of the production of this eminent 
artist were presented at the Great Exhibition In Hyde Park, in 
1851. They consisted of ten bands, each composed of a certain 
number of parallel lines ; those in each band being closer together 
than those in the preceding one. In the following table, we have 
given in the second column the number of lines which would fill 
the breadth of an inch in each succeeding band in one of these 
specimens. 
I. .... 
. 11265 
II. 
. 13142 
Ill. 
. 15332 
IV. .... 
. 17873 
V, . . . . 
. 20853 
VI.. 
. 24309 
VII. . . 
. 28433 
VIII. ... 
. 33153 
IX.. 
. 38613 
X. .... 
. 49910 
Thus it appears that, in this specimen, the closeness of the ruled 
bands varied from 11000 to 50000 to the inch. 
These bands are ruled on glass in parallel directions, being sepa¬ 
rated band from band, by comparatively wide intervals, so that, 
if sufficiently magnified, they present such an appearance as is 
shown in fig. 24. The highest band being that in which the lines 
are most separated, and the lowest that in which they are closest. 
It is very difficult to convey a correct idea of the real appearance 
of this system of engraved bands before it is magnified; let us 
suppose, however, that fig. 23 represents the real magnitude of the 
slip of glass upon which the engrav¬ 
ing is made, and that the white 
circle in the centre is the part of the 
glass across which the series of ten 
bands, shown in a magnified form 
in fig. 24, are drawn. The entire 
space occupied by all the ten bands 
will then be less in width than the black line which is drawn 
across the white circle in fig. 23. It must not be imagined that the 
white circle in fig. 23 represents that shown in fig. 24, the latter cor¬ 
responds with a minute circular space in the centre of fig. 23, not 
much greater in diameter than the breadth of the black line. 
28. Various other test-plates have been engraved, and put in 
circulation by Mr. Nobert; I subjoin the analysis of one consisting 
68 
Fie*. 23. 
