SOLAR CHEMISTRY. 
211 
readers acquainted with the fact; that we may, by burning 
certain mineral substances, produce very intensely coloured 
lights. Soda, or common culinary salt, gives a monochromatic 
yellow ; strontian produces the red fires of our theatres ; barytes, 
the pale green of ghost scenes : copper burns with a green 
flame ; iron, with a yellow-brown one ; and hthium with a 
brilliant crimson. Now, if these flames be examined through 
a prism, or if a concentrated pencil from those artificial sources 
of coloured light be passed through one, we obtain well- 
marked spectral images, some of which are represented on the 
accompanying drawing. 
1 is the Solar spectrum, with its principal black lines, those 
marked with capitals being the more important. 
2. (Na.) The bright yellow line produced whenever soda, in 
any form, is present in the source of light. 
3. {Sr.) The interesting series of bands produced by 
strontian. 
4. (Cy.) The spectrum obtained when chloride of calcium, or 
any of the salts of lime, are subjected to combustion. 
5. (Bq,.) The spectrum produced by the barytes salts. 
6. (K.) The spectrum observable when potassium or any of 
the salts of potash are vaporized in a flame. 
The woodcut annexed, shows the extension of the — w 
solar spectrum to the end of the fluorescent rays. 
This is given to prove on the authority of Professor 
Stokes, that these most highly refracted rays have 
a larger number of inactive dark spaces than the 
more decidedly luminous rays possess. We have 
yet to examine, with the closest care, the relation of 
those lines to our own atmospheric influences. It 
is necessary, therefore, to observe much caution in 
receiving the evidence which has been brought for- 
ward in proof of the solar origin of those strange 
bands. But let us examine the proofs. 
Kirchoff and Bunsen lay great stress upon the 
sodium spectrum, as proving the extreme delicacy 
of this mode of analysis. The yellow line — the 
only one seen— is coincident with the dark line D 
of Fraunhofer. This beautiful bright yellow hne is 
observable when less than aovook, ooo th of a part 
of soda smoke is mixed with air. From the cir- 
cumstance of the air of these islands, having 
almost always some saline matter floating in it, the 
yellow line of the sodium spectrum is rarely absent. 
The lithium spectrum has not been represented on 
our plate ; but it gives two sharply defined hnes : one 
a bright red, the other a yellow one — the former 
apparently corresponding with line five between B 
