228 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
phire, at prices ranging from 4 to 10 shillings a carat, according to 
color, quality,-and size. 
inate cs may be their economic importance, a very much debated 
question, there can be no doubt as to the scientific interest of this 
group of artificial gems. In the first place it is a matter of some 
interest that a mass of fused material formed in this way should not 
only be crystalline but possess all the characteristics of a single 
crystal. Crystallographers are agreed that each boule is a single 
crystalline individual, with the axis roughly perpendicular to the 
plane of formation; that is to say, running from the point of attach- 
ment of the pedestal to the top of the mass. On the top of the boule 
one invariably finds a mass of symmetrically arranged facets, which 
Dr. Herbert Smith has found to correspond with the fundamental 
rhombohedron of corundum. Judging by analogy with other mate- 
rials, one would expect at first sight that a fused mass formed in this 
way would be either a heterogeneous mass of minute crystals or 
entirely amorphous, possessing the structure characteristic of glass. 
It is well known, for example, that under similar conditions pure 
silica yields ‘quartz glass,’’ which is extensively manufactured at 
the present time. Oneis tempted to dwell upon this point, and discuss 
its bearing on such matters as the devitrification of glass, but it would 
be entirely out of place to do so in the present paper. 
Then, again, there is the matter of coloration. One would like 
very much to know what is the state of combination of the chromium 
in a ruby, and whether the color is produced by chromium aluminate 
in solution or metallic chromium in molecular suspension. In glass, 
as is now well established, this color is produced by the optical effect 
of ultramicroscopic spheres of metallic gold or copper, but there 
seems to be no parallel between the two cases. 
A point of more practical interest is the fact that although the 
artificial corundum is a true crystal it possesses the shape and forma- 
tion of:a congealed liquid or glass. The practical interest of this lies 
in the fact that it affords the only means of distinction between this 
artificial corundum and the naturally formed gemstone. Being of 
exactly the same composition and crystalline structure as the natural 
mineral, it can not be identified by any of the physical tests I briefly 
referred to above. For all practical paper the artificial ruby is a 
ruby, and one can only deny that it is a ‘‘genuine ruby” if this word 
is held to connote essentially a product fede in the earth and not 
made by man. 
And yet, owing to the curious anomaly of its pce the artificial 
product can almost invariably be distinguished from the natural 
with the greatest ease. In the naturally formed stone any foreign 
matter which may be present is coerced into following the lines 
of growth of the crystal, and more particularly bubbles of gas which 
