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POPULAR SCIENCE REVIEW. 
topaz, fragments of quartz, grains of chromic acid (chrome-iron ?) and 
titanic acid, and globular bodies of a very high refractive power, which he 
believes to be diamonds. Mr. J. Torry, in a single sample of the sands 
washed from the gold ores of Nicaragua, found twenty mineral species, some 
of them very rare. 
A Huge Diamond. — We learn from “ Silliman’s Journal” for April, that 
a diamond weighing 288^ carats, and of the first water, was found Nov. 6, 
1872, at Waldeck’s Placer, Vaal river, South Africa, by Robert Spauld- 
ing’s party. It is stated to measure about inch in diamater. If this 
statement is confirmed, the Waldeck-Spaulding diamond is among the largest 
rough diamonds of which we have mention. The Regent weighed 410 
carats (136|| cut), and the Great Mogul 780^ carats (279 jg cut). A dia- 
mond in the possession of the Rajah of Maltan, in Borneo, weighs 367 
carats ; the Nizam belonging to the King of Golconda weighs 340 carats. 
The American Mining and Scientific Press ” of Feb. 22, gives a figure 
of the Waldeck-Spaulding stone, taken from a photograph, which shows its 
form to be an irregular octahedron. 
Herr F. Hessenherg's Mineralogical Researches are of great interest and are 
not yet completed. In No, 11 (which is in vol. viii. of the Proceedings 
of the Senckenberg Nat. Hist. Society of Frankfort ”), he continues his 
crystallographic researches. He describes crystals of perofskite from 
Pfitschthal, of calc spar from Iceland and Andreasberg, and others of sphene 
and axinite j indicating for sphene some evidence of hemimorphism. 
MICROSCOPY. 
Structure of Eupodiscus Argus. — According to Mr. Samuel Wells 
(U.S.A.), who has a paper on this subject in the Monthly Microscopical 
Journal ” for March. He says that the valve of Eupodiscus Argus is 
remarkable for its opacity, its thickness being about it presents 
therefore, a beautiful appearance as an opaque object with a binocular. The 
structure of the outer or convex surface can be readily made out with a low 
power. It is dotted with depressions irregular in size, shape, and arrange- 
ment ; between these depressions the surface rises in ridges, which glisten 
and sparkle like fresh snow. No arrangement of light (except transmitted) 
varies this appearance. The depressions are unmistakable, and, as appears 
by the use of the binocular, and the examinations of the edges of frag- 
ments, are pockets extending nearly, but not quite, through the valve. The 
average diameter of these depressions is about inner or con- 
cave surface is much more difficult of resolution j its structure is quite 
different to that of the convex surface. It is nearly smooth, has no ridges, 
and (probably) no granulation. It is covered with round dots, radiating 
irregularly from the centre, and leaving irregular blank spaces between the' 
rows. It is probably this surface that is figured by Mr. Slack, who makes 
no mention of any difference between the two surfaces, but appears to have 
made the drawing from a specimen on Moller’s typen platte. In my typen 
platte there are the eighteen-corner Eupodisci, and three others, and all 
were mounted concave side up, which is the easiest mode of mahing them 
