Page:Popular Science Monthly Volume 36.djvu/716

698 this soon came under consideration, both accidental color which follows an impression and that caused by juxtaposition. He simplified the subject greatly by making this division of the subject, the first class including all appearances which succeed the contemplation of a bright-colored object, the second those which accompany such contemplation. The phenomena had been observed before, but Plateau was the first who reduced them to law.

Some valuable experiments and formulated theories on the subject of irradiation were begun, but was interrupted by his oncoming blindness.

Before this time, Plateau's attention had been fixed by the spherical form which a drop of oil assumed when introduced into an alcoholic liquid having the same specific gravity as the oil. From this small beginning he developed a most wonderful series of experiments and laws under the title "Memoirs upon the Phenomena which a Free Mass of Liquid presents when removed from the Action of Gravity." Eleven papers upon this general subject appeared between the years 1843 and 1868 in the memoirs of the Academy of Brussels. These included his experiments upon films and the formulation of the laws which govern their union—one of Plateau's most valuable contributions to physical science. He also made some very interesting investigations upon liquid jets, with a number of shorter papers and notes upon various subjects. Most of these papers appeared in the memoirs or bulletins of the Academy of Brussels, a few in the French and German annals of science, "Comptes Rendu de l'Académie des Sciences de Paris," and Poggendorff 's "Annalen." He died September 15, 1883.

It is impossible to read of Plateau's work, carried on for so many years in spite of frail health and total blindness, and not draw a parallel between Huber and himself each of them a man who was the peer of any worker in his own field, though so cruelly handicapped. They are two of the purest, noblest, most pathetic, most heroic figures who adorn the annals of science.

believing it premature till some new groups of lines are further studied to express more than provisional suggestions as to the nature of certain nebulæ he has been examining spectroscopically, Mr. Huggins supposes that they may represent an early stage in the evolutionary changes of the heavenly bodies. They consist probably of gas at a high temperature and very tenuous, where chemical dissociation exists, and the constituents of the mass are arranged in the order of vapor-density. But the stage of evolution which the nebula in Andromeda represents is no longer a matter of hypothesis. Recent photographs show a planetary system at a somewhat advanced stage of evolution. Already several planets have been thrown off, and the central gaseous mass has condensed to a moderate size as compared with the dimensions it must have possessed before any planets had been formed.