698 THE POPULAR SCIENCE MONTHLY. 



this soon came under consideration, both accidental color which 

 follows an impression and that caused by juxtaposition. He sim- 

 plified the subject greatly by making this division of the subject, 

 the first class including all appearances which succeed the con- 

 templation of a bright-colored object, the second those which ac- 

 company 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 on- 

 coming 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 Phe- 

 nomena 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 vari- 

 ous 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'Acade'mie des 

 Sciences de Paris," and Poggendorff 's " Annalen." He died Sep- 

 tember 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. 



While believing it premature till some new groups of lines are further studied 

 to express more than provisional suggestions as to the nature of certain nebula? 

 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 repre- 

 sents is no longer a matter of hypothesis. Eecent 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. 



