=3. Spectroscopic Analysis.= We have next to deal with the constitution of the sun, or the nature of the substances of which it consists, and for this purpose we must first understand the operation of the spectroscope, in many respects the most wonderful instrument that man has invented. It has given birth to the “chemistry of the sun” and the “chemistry of the stars,” for by its aid we can be as certain of the nature of many of the substances of which they are made as we could be by actually visiting them.