corresponding to certain Points in the Solar Spectrum. 448 
This Table shows that the Newtonian values are not recon- 
cileable with those of Fraunhofer ; because they make the line B 
lie beyond the red, and the line H beyond the violet end of the 
spectrum. The cause of this discrepancy is traceable to New- 
ton’s having made his observations on an impure spectrum ; 
Fraunhofer having been the first to obtain the pure spectrum, 
produced by numerous fine equidistant lines, and from which 
his wave-lengths were determined. 
It is remarkable, however, that if we adopt Newton’s primary 
series without subjecting it, as he did, to the operation of taking 
the cube roots of the squares, we shall obtain from it values for 
the wave-lengths corresponding to the boundary lines of the seven 
prismatic colours, agreeing much better with Fraunhofer’s values 
for the wave-lengths corresponding to the fixed lines. 
This series, reduced to the standard of the French inch, stands 
as under :— 
Borders of colours. Fixed lines. 
Red. . . poimtov hae B 0:000025410 
“nino y0-000024004 C 0:000024235 
ous. yet Mean wave = pit ea 
Green |’. bone dba E 0-000019440 
Blue .°: eee ae F 0:000017915 
Indigo . ih SRA G 0-000015860 
Wiolet Liao ee H 0-000014575 
0:000013554.%* 
In this Table, not only are the fixed lines brought within 
the spectrum, but each is referred to nearly its proper position. 
It were desirable that fresh observations be made on the wave- 
lengths corresponding to the border lines of the colours in the 
pure spectrum, to ascertain whether these are accurately repre- 
sented by the above series, or whether some other must be found 
which shall more correctly exhibit their ruling law. The sub- 
ject is worthy of the attention of the British Association, were it 
only to prevent the existing error, in regard to the estimated 
value of these wave-lengths, from being any longer perpetuated. 
* This series makes the interval between the extreme violet and the ex- 
treme red as 1 to 2, corresponding to the musical octave. 
