THE RARE EARTHS.—MAGEE. Ixvil 
same trouble, too, is one of the chief reasons for the appearance on several 
occasions of pseudo elements which, obtained with extreme difficulty, 
seemed to have a fair claim to separate existence, and which required 
considerable time and skill to prove their non-existence. 
Let me illustrate. You are all aware that in the case of our ordin- 
ary elements there are sharp points of separation. HCl. throws down 
from a silver salt solution all (or nearly all, for this reservation must be 
made in the light. of refined methods) the silver as AgCl. H,S throws 
down from solution a large number of sulphides even in acid solution we 
must grant, but for every one of these elements there is some known 
reagent or some exact method of treatment, which affects one and ouly 
one of these elements. There are, undoubtedly, difficulties in exact 
separations, but a fair analytical chemist can always separate them. 
With the rare earths, however, each reagent seems to act so similarly that 
there is no sharp line of demarcation, and the only methods applicable to 
their separation are slow and remarkably difficult of application. Abso- 
lutely quantitative analytical processes are unknown, and no results 
published in the various mineralogical books as giving the composition of 
the minerals containing them are reliable. I put forward no claims to 
superiority as an analytical chemist, but I was occupied from October Ist 
to the Christmas vacation, with all the advantages of a well equipped 
laboratory at my disposal, in obtaining 11 grams of pure Ceria, using a 
method proclaimed as the best to date, but acknowledged to need, as my 
experience also confirms, a seven times repetition to ensure so-called 
purity, and leaving behind the suspicion that, as it was purified according 
to the standard of a vanishing test, it was even then not absolutely pure. 
Yet this subject has received some of the best thought of the ablest 
chemists of the world during the past 50 years. Bahr, Bunsen, Rammels- 
burg, Wolf, Wing, Gibbs, Wohler, Popp, Crookes, Marignac, Delafon- 
taine, Boisbaudran, Nilson, Cleve, Kruss, Bettendorf, Welsbach, in fact 
all the advanced inorganic chemists of the past half century. There is 
no discouragement, the fight goes on with that grim determination to 
succeed which only the scientist knows. What have they accomplished 
for the world? Not much in this line! But if these were all the 
scientist strove for, our discoveries and advance would be of a low order. 
Indirectly, the close study and wide experience with reagents and 
methods has led to many useful results, but we need not linger over this. 
Throughout all the period during which Ni. an Co. have been known, 
there was no ready and direct method of separating them ; but a few 
