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But when the spectroscope had done that, its work was not finished, for it has not only told us what the stars are made of, but another thing which we could never have known without it namely, if they are moving toward us or going away from us. You remember we have already remarked upon the difficulty of telling how far one star lies behind another, as we do not know their sizes.
Several diversely-coloured images of them are formed in the spectroscope; each may be seen under a crimson, a yellow, a green, and a deep blue aspect. Friedrich Zöllner was, by a few days, beforehand with Huggins in describing the open-slit method, but was somewhat less prompt in applying it.
But when the paper goes on to speak of the actual chemical nature of the sun-spots, as tested by a spectroscope; to tell of a "cool" stage when the vapor of iron furnishes chief spectrum lines, and of a "hot" stage when the iron has presumably been dissociated into unknown "proto-iron" constituents then indeed does it go far beyond the comprehension of the keenest eighteenth-century intellect, though keeping within the range of understanding of the mere scientific tyro of to-day.
"If you want an opinion from me," I said, with a laugh, "you'll have to tell me first what I am looking at." "That," he explained, as I continued to gaze, "is one of the latest forms of the spectroscope, known as the interferometer, with delicately ruled gratings in which power to resolve the straight, close lines in the spectrum is carried to the limit of possibility. A small watch is delicate.
The spectroscope 'spots' the substance, to use a police idiom, the moment the case is turned over to it. There was no poison there." He had raised his voice to emphasise the startling revelation. "Instead, I found an extraordinary amount of the substance and products of glycogen. The liver, where this substance is stored, is literally surcharged in the body of Phelps."
When a piece of glass like this is fixed in a telescope in such a way that the sun's rays fall on it, then there is thrown on to a piece of paper or any other suitable background a broad coloured band of lovely light like a little rainbow, and this is called the sun's spectrum, and the instrument by which it is seen is called a spectroscope.
When the spectroscope was first available for stellar research, the leaders in this branch of astronomy were Huggins and Father Secchi, of Rome. The former began by devoting years of work principally to the most accurate study of a few stars. The latter devoted the years from 1863 to 1867 to a general survey of the whole heavens, including 4,000 stars.
"Ebulae," he might say; "yes, they were a specialty of mine; but swarms of meteors I know nothing of these. And 'spectroscopes, 'photographs' what, pray, are these? In my day there were no such words or things as spectroscope and photograph; to my mind these words convey no meaning." But why go farther? These imaginings suffice to point a moral that he who runs may read.
In 1868, when Lockyer first directed his spectroscope to the great flames or prominences that rise thousands of miles, sometimes hundreds of thousands, above the surface of the sun, he instantly identified the characteristic red and blue radiations of hydrogen.
The results of analysis by the spectroscope of the light emitted by certain elements at different temperatures may be reasonably interpreted by supposing that these elements are separated into simpler substances by the action on them of very large quantities of thermal energy.
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