a 
4 vs 
— 
: 
: 
120 sOME RESULTS OF AN ASTRONOMICAL EXPERIMENT 
alongside of it. I have several times suspected that it was 
double, and now I am almost sure of it. D3 sunset nearly 
of lig 
9° 55 ° m. on ne 21st, I can see all the eight lines between the 
rning is warm and hazy, and a goo deal of cloud 
about, sree; | in the direction of the sun. 11h. 10m., the air 
lines are rapidly fading ; line 4 does not seem changed, but the 
ible 
Measures of the lines beeen the two Ds mean of three taken 
and 21st October, 5 The measures are taken from line to 
line, and represent ae of the micrometer. The whole distance 
Dit 
o D2 is cov oe a Aa ia glee of a ura el 
et 336 | 266 | 360 | 1356 | 208 | 956 | 20] 346 | isi} cae 
Some of the members present may remember that, when I 
rotught my Sydney measures of the D Tine before you ‘inst Keim 
produced a copy of Dr. Huggins’s drawing of the es at 
Ostord: and those of Colonel Campbell at London. Since thes I 
have received from Dr. Hu gins a more complete and perfect 
copy of his drawing of the lines between the Ds and it 1s inte- 
resting to toes it with those observed here ; there is very little 
similarity bet is baal and mine. From Mr. i ilger 
bially clear atmosphere of our western , L was “the more 
anxious to test this “again of purity as means of the large 
troscope, and see if we might affirm that it stood the test. 
Now the facts aesich: I have brought before yon do this most. 
emphatically ; on a fine clear day, with dry wind on the moun- 
tains, at noon, there is not a single line due to the absorption of 
the e atmosphere i in the part of it examined ; but as the sun sinks 
sea, and at once the lines a < Lore at noon. Of course I one 
bork dealing with only a small fraction of the solar spectrum; to 
take the whole in such detail would require the labour of a life, 
