Measuring and Becording Spectrum Bands. By T. Palmer. 283 
M. 
A. 
Observations. 
1. 21-23 
Middle 
568-9 
[Sharp, very black, 2 divisions in size, 
< ends and centre equal. 
[ Near D. 
2. 20-45 
517-25 
iSliarp, black, 1 division in size, ends and 
< centre equal. 
1 Near E. 
3. 20-79 
ji 
504-75 
[Sharp, shaded, 1^ divisions in size, ends 
< and centre equal, 
( Near h. 
4. 19-77 
474-25 
(Sharp, shaded, | division in size, ends 
< and centre equal. 
( Near F. 
5. 18-32 
55 
460-00 
ikjuctip, ftuducu., ±-g- uivisiuLi 111 biioe, eilub 
\ and centre equal. 
6. 17-65 
55 
432-12 
[Sharp, black, 3 divisions in size, same 
<^ as No. 1. 
( Near G. 
And now with respect to mapping the spectra and drawing the 
charts, the plan which I have adopted is a very simple one ; thus I 
first of all produce an exact facsimile of what is actually seen, as 
compared with the result of some different substance, somewhat 
approaching it in resemblance or otherwise, then by means of the 
micrometer scale produce the bands in a succession of lines, the 
thickness of which is shown by the brackets, you have then only to 
refer to the tables and to affix the wave-lengths, in which case, 
as seen on again referring to the drawings, they are marked 
on the top, whilst the micrometer divisions are recorded below. 
The absorption bands which are shown on the top of this scale 
represent those of the first spectrum or that of the object on 
the stage of the microscope, whilst the underneath are those of 
the second, or the spectrum of the object on the side or com- 
parison stage. ♦ 
And now what has taken many months of hard work has 
been expressed in a few minutes, I hope to your satisfaction. There 
has of necessity been some repetition, but I thought it advisable to 
lay down in an explicit manner the main principles as to how I 
work, that similar results, with equal success, may be obtained by 
other observers in this most interesting and, I am afraid, somewhat 
neglected branch of microscopy. However, my purpose in ending 
thus is, first of all, to thank you for the kind attention you have 
given me ; and, finally, that 1 may retire with the hope of being 
