corresponding to certain Points in the Solar Spectrum. 441 
Ist Ser. o=1°751099 2nd Ser, 0=1°735549 
7=1°248298 7=1'245244 
2:999397 : 2:980793 
Thus in both cases the sum is very nearly 3, but considerably 
nearer in the first than in the second; and as 0+4+7=:8 is a very 
convenient relation, this may be viewed as a third advantage 
presented by the first series, which requires only a trifling altera- 
tion to make it fulfil this condition, as well as that of having 
0, m7, o, w in arithmetical progression. These advantages 
afforded by the first series overweigh the single advantage fur- 
nished by the second, of presenting the before-mentioned rela- 
tion of lpi ee H;), which is of little comparative value ; 
whereas the relations presented by the first series, when per- 
fected, afford the great facility of rendering the whole of the 
wave-lengths deducible from that of either B or D alone. 
The first series, when properly adjusted to the several relations, 
B°=D*, BD =E" o=7 +0222), w=0 +0222! c= +0:222', 
and o+ 7=8, will stand as under :— 
Logs. Nos. Differences. 
= 0°2436268 1°752374 
= 0°1847346 1:530152 0222222! 
Se pas EAE oem 
= 7930 0:0381877 
= 0:0960845 1:247626 0:0603804 
= 0:0886501 1°226451 0:021175 
gd = 0:0848012 1:215630 0010821 +0:222222! 
= 0:0490882 1:119665 0:095965 
ar = 0:0357130 1:085708 0:033957 | 0-666666! 
It will thus be perceived that, while the terms of the series are 
nine in number, they are divisible into three groups; that the 
sum of the first and middle term is 8; that each of the common 
differences is 2 and their sum 2,—+elations sufficiently remark- 
able in themselves, and easily borne in mind. 
The following are the values of the wave-lengths correspond- 
ing to the fixed lines as deduced from the above series, and as 
compared with the first set of observed values:— 
eaqnyeo 
eR 
Calculated. Observed. Differences. 
B 2540844 2541000 —0000156 
C 2423694 2425000 —(0001806 
D 2175112 2175000 +0000112 
E 1942645 1943000 — 0000355 
F 1789289 1789000 +0000289 
G 1583957 1585000 —0001043 
H 1449944 1451000 — 0001056 
