86 
EDWARD S. SIMPSON, B.E., F.C.S. : 
There is a great range in the chemical and physical 
properties of the rare metals, practically every known group 
of the metals including at least one rare member. In- 
dividually and collectively they are a most fascin ating com- 
pany. The most positive (basic! metal known, viz., caesium, 
appears in the list, as also several of the least basic, such 
as niobium ; the heaviest metal, osmium* * * § , and the lightest, 
lithium,f, are here ; the most noble metals, iridium, rhodium 
and ruthenium, and those most easily affected by chemical 
agents, caesium and rubidium. The most fusible of all 
metals, except mercury, are “ rare,” viz., caesium and 
gallium ; the most infusible, tungsten, has only recently 
been removed from the ranks of the rare metals, which still, 
however, number amongst them several which can onfy be 
melted in an electric arc, and also a metal, beryllium, 
which is not known to liquefy, but which passes direct 
from the solid state into the gaseous. 
General Distribution of the Rare Metals. 
Little is known of the extra-terrestrial distribution of 
these elements, but what little is known points to their 
being rare not only terrestrially but also cosmically. This 
is a fact of deep significance. Our only means of recognising 
any elements beyond the confines of the earth are, first, the 
spectroscopic study of the light emitted by self-luminous 
heavenly bodies, and, secondly, the analysis by various 
means of those extra-terrestrial bodies, meteorites, which 
at rare intervals fall onto the earth’s surface. 
No less than fifteen rare metals have been detected 
with certainty in the sun.j They are : — 
Beryllium Cadmium Yttrium 
Scandium Erbium Cerium 
Lanthanum Neodymium Zirconium 
Germanium Vanadium Niobium 
Molybdenum Rhodium Palladium 
Eight others are of doubtful occurrence, viz. : — 
Lithium Thorium Tantalum 
Cranium Ruthenium Osmium 
Iridium Platinum 
Cadmium has been reported in the star AlphaCygni§, and 
in the nebula in Orion ; thallium in the Great Comet of 
1882II ; vanadium in Arcturus^j. 
* Specific gravity, 22.4. 
| Specific gravity, 0.59. 
; J. I anclauer : Spectrum Analysis, p. 200. 
§ N. Lockyer : The Meteoritic Hypothesis, pp. 287, 396. 
|| Ibid., p. 222. 
II W. S. Adams: Astrophys Jour. XXXII 1. 
