Reviews—Origin of the Diamond. 327 
remainder being evidently varieties of previously known species, or, 
because of the incompleteness of the investigation, doubtful. The 
introductory pages contain also a list of the principal literature 
published during the period in question, a special section being 
devoted to the literature on the subject of X rays and crystal 
structure, which constitutes the most striking advance of recent years 
in the method of investigating the structure of crystals. In order to 
retain the book within moderate dimensions, the information given 
under each mineral species is. kept as concise as possible, and 
illustrations are only added in the case of the more interesting 
species. Under the heading ‘‘ New Minerals” are given a number 
of incompletely described minerals which are considered to be new, 
but have not been named. It was not found practicable to re- 
calculate the angles and other data given, and the particular author's 
published values were accepted in every instance ; errors creep in so 
easily that an independent check, as was the practice with the Danas, 
would have been very valuable. 
Mineralogists will feel a debt of gratitude to Professor Ford for 
taking up the task perforce relinquished by the younger Dana. 
Il1.—Oriern or tHe Diamond. 
N original and highly interesting paper on the origin of the 
diamond, by David Draper and W. H. Goodchild, is to be found 
in the Mining Journal for May, 1916. We have not the space to go 
into the details of the author’s remarks, but must content ourselves 
with quoting their conclusions :— 
1. A kimberlite pipe does not differ essentially from an ordinary 
voleanic vent. 
2. The lava is derived from an infra-granitic zone basaltic in 
character, eclogite, but the original lava is not necessarily either 
. ultra-basic or highly peridotitic. 
8. Minute diamonds may be present invariably as an accessory 
mineral in the eclogite from which the pipe material is derived, but 
the evidence on this point is inconclusive. 
4, Towards the end of the active period of vulcanicity differentia- 
tion of the magma in the vent is brought about by the sinking of 
early formed crystals, principally olivine and ferro-lime pyroxenes, 
thus producing an ultra-basic mass in the lower regions of the vent. 
The ultra-basie character of kimberlite is thus due to magmatic 
differentiation, and not to a primary derivation from an ultra-basic 
source. 
5. After freezing of the magma in the upper regions of the vent, 
the molten residuum beneath the solid plug continues to be slowly 
impregnated with magmatic gases, chiefly water and carbon dioxide, 
thus hydrating the melt, lowering its viscosity, and prolonging the 
solidification period, and at the same time effecting extensive 
serpentinization. The serpentinization is thus due to a solution of 
carbon dioxide in water under pressure and introduced from below, 
and is not the result of weathering by downward percolating 
solutions. 
