Aucust 24, 1899] 
NATURE 395 
very much simpler one than it appears to be at present, 
and it may possibly break down that terrible amount of 
uncertainty and irregularity which it has been my duty 
¢o point out to you in the series so far examined. 
there is no fluting from one end of the spectrum to the 
other.. 
Rydberg has suggested that an investigation of the 
so-called “longest-lines” of the various substances may 
| 
a au. 22 
a a eS Principal series. ist and 2nd subordinate. SoM) as | = 
= a |3\2 29) a3) Ej 
ey ae SEE ss] Bg 
pe 2 “ |"s REMARKS. 2Ey) 3 te pe 
(|) Boe. | ie iva 3! 
= 2 | 3 | Single. | Double. | Triplets.|Single. | Double. | Triplet. fetch |b 2 a 
y | | Z fase 
| | + | 
Hyprocen | — | 1/]3)|1] — |Double?) — — | Double} — — Ioo | 100 | — 
| | | Insub. series the double 
ly oxt| } represents strong mem- 
} | ber with faint com- 
HELIUM ... ae esnier| Single — = — |Double) — panion. Helium really) roo | 100 | — 
ASTERIUM — | — | 3] rt |Single = — |Single — — gives a spectrum of six, 100 | 100 | — 
| series, but one set of| 
| | three series has been) 
| | called Si Es 
Eeeros } 70°| 3,\.1 | — | Doubler) ~— — |Double?) — 100 | 100 | 180 
ODIUM.... ||| 230/3/1 = | Dou — | Double} — 100 | 100 | 90 
Porassium | +I. 39:0 3/1] — | Double} — | — | Double] — pee eae a alll c25¢9) 6a7|b100 58 
RUBIDIUM Sear |r | — | Double = Not observed Spe rcnG roo ieies 8 
| 5 weights increase. 3 
Castum... | J 1353) 2) 0 | — | Double) = Not observed 100 | 100 62 
| Each element contains 
Copper ... | 1634 /2]/o0| — = — — | Double = [ in the ultra-violet a) 6 — |1080°5 
SILVER Ir 1076 | 2/0] — — = — | Double = | very strong pair of lines) 26 | — | 960 
GoLp 1967 |o}/o0| — = = | Sj) Se -) = { which may be prin-) ? — |1061°7 
| | cipal series. 
| 2852°2 and some pairs 
MAGNESIUM |) amen nO: —. || ao an — ~-  /|Triplets|+ not picked up by these| 64 55 | 600 
| | | series. 
| | | (Some more triplets and 
CALCIUM Tesg| 2 io! — | = — — — Triplets} pairs not picked up by| 34 17 | 700 
| | these series. 
STRONTIUM | Rreaezalkon|| = | tes — _— — . |Triplets = 20 7 | 700 
Barium ... 1368 }o]/o0/ — | = = — —- | = = =) =o) 25 
ZINC | 651/2}/o0} — | — = — — Triplets (ae, each “case ben eae 80} 43 | 410 
CapMIUM I \rrr7|2\);o0); — | = = = — Triplets pene Ei binaeceeent 50 | 14 | 320 
MakeuRy if aieelro| = | ay ia Tri iets, | line in the ultra-violet 27 |12°5 |—40 
| pretS\. may be principal series. 
ALUMINIUM | | S720) | — = — = | Domi) = — — | 25 | 654°5 
INDIUM ... FILE. |113°7 | 2 | 0 — _ _ — | Double — — — 25 | 176 
THALLIUM | 203°77|2/o0| — — — | — | Double} — | — —| 17 | 282 
| | | (No series have been 
SEUNG. « liv 117‘°8 | 0]}0 —- |) =— -- —} — — || discovered, but there) — — | 232 
LEaD ... | f° |206%4 |o0}/0/ — | — — _ —- |} = seem to be groupings) — | — | 326 
ARSENIC | 74°9|/0}/0] — — — — == = of lines which recur) — | — | 450 
ANTIMONY | ;V. |1196/0/0/ — | — | very frequently. The — | — | 629°5 
BIisMUTH i) 207°5|9}/o0} — — — —_— —- | = lines do not form) —J| — | 270 
series. 
OXYGEN. J. 15°88} 6 | (2)) — — {@riplets;) — | —_  |Triplets — Yh = = 
: | lea These probably have} 
. Vig) | six series. One strong 
SULPHUR Bio!3 |r) — — Triplets) — | — (Triplets|) triplet is observed) — | — | 114 
SELENIUM | Fry || 3.) I — — Triplets) — — |Triplets|) which may be prin-| — | — | 217 
| | || cipal series of second 
| set of three series. 
} 
Another matter of considerable importance to us in 
attempting to arrange the chemical elements along this 
line of series—and it is work that is sure to be done now 
that the matter is once started—is to endeavour to see if 
there is any strict relation between those chemical sub- 
stances which give us these simple series and those 
which are more apt to provide us with those exquisite 
thythmic flutings. In some of the elements the flutings 
and the proportions of them from one end of the spec- 
trum to the other are very remarkable, but in other 
metals the wonderful thing about them is that practically 
NO. 1550, VOL. 60] 
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eventually help us in our inquiries. I will tell you what 
the longest-line means. If we examine a light source 
by pointing the spectroscope directly at it, of course the 
rays from every part of the light source enter the instru- 
ment ; but if we throw an image of the light source on the 
slit of the spectroscope, then those particles which exist 
furthest from the centre will be visible furthest from the 
image of the centre, and therefore if they are visible 
enough to give spectra, we should get long lines stretch- 
ing from the centre to the very limit at which their light 
is visible enough to be utilised by the instrument. As a 
