MEMORANDA. 
TABLE. 
Number of lines in 
Distance of tlie lines in parts 
each 
band. 
of an English inch. 
De la Rue. 
G. H. 
De la Rue. 
G. H. 
1 
7 
7 
Txifi T 
1 
1125 0 
2 
8 
8 
1 
13 330 
3 
9 
9 
1 
, T5"4 2 6 
1 
15'500 
4 
10 
10 
1 
, 181 el? 
1 
18000 
5 
11 
12 
. "SOFT'S" 
2"03"0'0 
6 
1 'X 
1 
. . 2 3 4^ 1 
1 
2 3T50 
'7 
1 
15 
15 
1 
2 8 1 .5" 3 
2"8"3"0 0 
8 
17 
18 
3"'2'r^'S' 
■JlJ'io 0 
9 
19 
20 
1 
3 75 00 
10 
21 
21 
4""0¥3 0^ 
4tJoO 
11 
23 
23 
1 
43 05 0 
1 
45000 
12 
24 
25 
1 
4 7 3 2 7 
. 4T66 0 
13 
26 
25 
1 
.5 005 0 
n 
5 1000 
I did not attempt tlie last two series, as I found it very 
trying to tlie eyes when tlie lines approximate so closely. 
The lines were viewed by a very fine -j^th of Powell and Lea- 
land' s_, in my possession, mounted on one of Smith and Beck's 
stands, using their third eye-piece, the draw-tube being pulled 
out three inches in drawing the last three series ; and I think 
it says much for the steadiness and perfection of Smith and 
Beck's stand (though only their smaller one. No. 2, on a 
single pillar), that under these high powers I was able to use 
the camera with ease and complete absence from tremor. 
The lines were illuminated by Messrs. Smith and Beck's 
achromatic condenser during the whole of the time that I 
made this drawing. I find that the smallest black stop, for 
cutting off the central rays in the revolving diaphragm of 
their condenser, when it is placed a very little on one side of 
the position concentric with the axis of the condenser, shows 
the finer lines with a sharpness and certainty which I have 
failed in producing by other methods of illumination which I 
have tried. In conclusion, I will add, there are several irregu- 
larities in the intervals in that part of the diagram which 
represents the lines as drawn by the camera, but whether 
these irregularities represent corresponding ones in the lines 
