292 
and pure as the narrowest slit, the elimination of reflections of adjacent 
portions of the spectrum from the sides of the prisms, and the non-employment 
PROFESSOR PIAZZI SMYTH ON 
generally of any coloured glass screens could make it. 
The spectroscope was an experimental one prepared by myself. 
Colour of the 
Continuous 
Spectrum at 
the Place. 
Ultra- 
Red. 
Crimson- 
Red. 
| Crimson- 
Red. 
Appear- TEAC Differences. 
, b rs ied DAT! Chemical-origin-|| Concluded 
Object > bees et etary) ke black, fixed eer raph ieal SRE " from : ana oon WAVE. = a g 
\ raphe eee \para- ngstrom Ss Angstrom, NUMBER- eS S, 
Ofine tive Rev Grating Nor-| Thalen, &c. PLACE, per |i og | 
y symbol. mal Solar British Inch. || 5 & a 
Spectrum. aR A 
At Lisbon in 1877, July ; and in part é 
revised there in June 1878. Time sane four, 
of observation generally near Noon, Sane 
when altitude of sun=70° nearly, i aribheees 
and thickness of atmosphere looked ee. ronnie 
through = 1:06 (a Zenith-atmo- Cane : 
sphere being assumed=1°00). This ie cope (Tempo- 
‘first portion was observed with ee Ca. : rary Con- 
the Aurora Spectroscope. _Disper- Ww. deW clusions 
sion=sometimes 14°, sometimes 33° ba 3 : only, up 
from A to H, mag. power of tele- RE PRS to great 
scope= 10. a Re iad A.) 
Light of Continuous Spectrum of Sun 
begins at Ultra-Red end of Spec- 
trum, at or near to, 48-296 27 800 
First line observed, a dark line on said 1460 
continuous spectrum, 2 | 49°721 (29 260) 29 260 
A strong line, called X, . a || 50144 |(29 680)| Unknown, | 29 680 "4 
but appar- 
ently Solar 
rather than 150 
Telluric. 
A fine, i.e. thin, line, il 50°333 (29 830) 29 830 
Ultra-Red ends and Crimson-Red on 
begins, more or less, approximately. (30 000) 
A fine line, 1 | 51000 30 480 
Haze intervenes and accompanies the 12 
next three lines, 0°5 er s 
Fine line, : 1 | 51°132 30 600 80 
Fine line, = : 1 | 51:208 30 680 40 
Fine line, 1 | 51°258 30 720 , 
120 
Ney ena Baer 51386 Chemical | 30 840 | ,, 
zk 2 | L | Beats yee seoy wien, | 89 Be0 | 
: nown, bu 
second side of, apparently 
Solar rather 110 | 
‘ : than Telluric. 1" 
Band of lines, whereof line 1, 3 | 51°527 30 980 | 
line 2, 2 | 51°601 31 030 505 
line 3, 1 51-674 31 090 60} 
line 4, 1 51°740 31 150 | 60 | 
line 5, 1 51°808 31 210 ae 
a 
Very faint line, supposed to be the Z | i 
of low Sun spectra, 1 ' 52°624 Probably 31 900 i 
Telluric. 870 if 
V.B.—When any of the above lines, Z excepted, are seen at all (in the high-sun spectrum), they are nsualiya 
seen very black; an effect in part probably due to the ultra-faintness of the background of continuous spectrum i. 
they are projected upon ; and, in part, to their being not telluric, but solar lines; so that instead of being seen at | 
their faintest, as the former are, they are seen, if not actually at their strongest, at least exceedingly strong, and | | 
stronger beyond comparison than acknowledged telluric lines, such as B and a, in a high-sun spectrum, through a — { 
minimum thickness of terrestrial atmosphere ; proper care being of course always taken by the phere to prevent | 
false glare of brighter parts of the spectrum entering the field with these lines. a 
| 
a ‘ LES =. —— a SE tr. — ta 
