CHEMISTRY. 



397 



and publishing notes of phenomena already known to Mr. Crookes,the 

 latter gives in this paper a preliminary notice and summary of his 

 studies, although in an unfinished state. Mr. Crookes holds with other 

 chemists the opinion that didymium is not a simple body, but has been 

 unable to split it up into the green praseodymium and rose-red neo- 

 dymium announced in 18S5 by Dr. Auer von Welsbacli. Mr. Crookes 

 thinks didymium will prove to be more complex than this indicates. 



The author, referring to his note-book under date March 3, 188G, finds 

 the statement that the " big blue line (A 451.5) is still unclaimed," and 

 this blue line proves to be characteristic of dysprosium discovered by 

 Lecoq de Boisbaudran. 



As a result of the spectroscopic examination of the fractionated 

 earths fromsamarskite and from gadolinite the author concludes that the 

 earth hitherto called yttria is a highly complex body, capable of being 

 dissociated into several simpler substances, each of which gives a phos- 

 phorescent spectrum of great simplicity, consisting, for the most part, 

 of only one line. The author admits that a hitherto unrecognized band 

 in the spectrum, by absorption or phosphorescence, is not of itself defi- 

 nite proof of a new element, but if supported by chemical facts, such 

 as he details, there is sufficient prima facie evidence that a new element 

 is present. Until, however, the new earths are separated in sufficient 

 purity to enable their atomic weights to be approximately determined, 

 and their chemical and physical properties observed, Mr. Crookes thinks 

 it prudent to regard them as elements on probation. He gives in tab- 

 ular form a list of these probationary elements, designating them by 

 the initial letters of the minerals (or bodies) didymium, samarskite, 

 and gadolinite, from which they are respectively derived, and by the 

 addition to the initials of Greek letters. The table also gives the mean 

 wave lengths of absorption lines in the phosphorescent spectra, and 

 other data. 



Table of rrobationary Elements. 



