And what did Rumford and Davy know of energy in its various manifestations as compared with the knowledge of to-day, of Crookes and Rayleigh and Ramsay and Kelvin? What would Joseph Priestley, the discoverer of oxygen, and Cavendish, the discoverer of nitrogen, think could they step into the laboratory of Professor Ramsay and see test-tubes containing argon and helium and krypton and neon and zenon? Could they more than vaguely understand the papers contributed in recent years to the Royal Society, in which Professor Ramsay explains how these new constituents of the atmosphere are obtained by experiments on liquid air. "Here," says Professor Ramsay, in effect, in a late paper to the society, "is the apparatus with which we liquefy hydrogen in order to separate neon from helium by liquefying the former while the helium still remains gaseous." Neon, helium, liquid air, liquid hydrogen--these would seem strange terms to the men who on discovering oxygen and nitrogen named them "dephlogisticated air" and "phlogisti-cated air" respectively.
Again, how elementary seems the teaching of Her-schel, wonderful though it was in its day, when compared with our present knowledge of the sidereal system as outlined in the theories of Sir Norman Lock-yer. Herschel studied the sun-spots, for example, with assiduity, and even suggested a possible connection between sun-spots and terrestrial weather. So far, then, he would not be surprised on hearing the announcement of Professor Lockyer's recent paper before the Royal Society on the connection between sun-spots and the rainfall in India. 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.
Or yet again, consider a recent paper contributed by Professor Lockyer to the Royal Society, entitled "The New Star in Perseus: Preliminary Note"--referring to the new star that flashed suddenly on the vision of the terrestrial observers at more than first magnitude on February 22, 1901. This "star," the paper tells us, when studied by its spectrum, is seen to be due to the impact of two swarms of meteors out in space--swarms moving in different directions "with a differential velocity of something like seven hundred miles a second." Every astronomer of to-day understands how such a record is read from the displacement of lines on the spectrum, as recorded on the photographic negative. But imagine Sir William Herschel, roused from a century's slumber, listening to this paper, which involves a subject of which he was the first great master. "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."