THE RARE EARTHS.—MAGEE. )xiil 
The full list of these earth elements includes Ce., Zr., Th., La., Sc., 
Yt. and Yb., which are looked upon by chemists as actually elemental, 
and Pd., Nd., Sm., Ho., Er., Ter., Th., De., Dp., Ph., and even others 
which appear to differ from each other as oxides and may, some of them 
at least, be elemental, but are probably in most cases mixtures of two or 
more elements. They are not, however, known in the elemental con- 
dition but only in the form of oxides and salts. Some few have been 
reduced to the metallic condition yielding then grayish-white metals, but 
in such small quantities, and with such doubts regarding their purity, 
that slight advantages have been derived from the reduction. 
Before considering the properties of these substances and discussing 
their importance in the periodic system, it will be well to look into their 
history. They were first brought to the knowledge of the chemical 
world during that period of remarkable activity at the close of the 18th 
and beginning of the 19th centuries. Probably the first time that any 
mineral containing these oxides in any considerable quantity was noticed 
was in 1751, when Cronstedt obtained from an iron mine in Sweden a 
sample of the mineral now known to mineralogists as Cerite, a silicate of 
Ce., La. and Di., containing as impurities or accessories, however one 
chooses to consider them, small quantities of other rare oxides, together 
with iron, alumina, lime and traces of Mn., and even other minerals. 
This mineral was first analysed by D’Elhuyar in the laboratory of the 
noted chemist Bergmann, and stated to be a silicate of Fe. and Ca. It 
may seem remarkable that, even in those early days of chemistry---this 
was in 1784—such an error as the mistaking of the trivalent oxides for 
the very common substance lime should occur, but if the experience of 
such a noted analytic chemist as Plattner, so late as 1846, be considered, 
all wonder ceases. This chemist analysed several times the mineral 
Pollux from Elba and, despite all his care, and he was renowned as an 
analyst, he could only get his results to foot up to 92.75 per cent., nor 
could any one explain the matter until Bunsen recognized a new metal, 
Caesium, in the water of the Durkheim salt wells and proved it to be 
of the alkali group thus closely resembling Na. and K Plattner had 
been reckoning Cs. with an atomic weight of 132 as K. with an atomic 
weight of 39, and neither he nor his contemporaries seemed capable of 
proposing the very simple explanation that there must be present a new 
element. This experience of Piattner’s and its explanation probably 
saved Winkler from a similar error in 1886 and gave him the credit of 
the discovery of anew element. Repeatedly analysing Argryodite, as 
