446 PROFESSOR HEDDLE ON 
The fullest account we have, however, is one by THomson (Philosophical 
Magazine, vol. xxxv.) of two varieties which he analysed from different parts 
of the bed of the Don. The first, he terms “ iron sand,”’—the second, “ iserine.” 
“1. Iron sand.—Iron black, magnetic, octahedric, brittle, easily powdered’; 
powder greyish-black; S.G. 4765; not acted on by acids; lustre feebly 
elimmering. 
Protoxide of Iron, . 85°3 
Red Oxide of Titanium, . : ; 9°5 
Arsenic, . : ‘ 5 : d ; : 
Silica, 1 
Alumina, 5 ; f 5 ( : 
Loss, ; r : ' : ; : 2°7 
“2. Tserine.—Iron black to brown, angular grains, larger than iron sand, 
lustre semi-metallic, fracture conchoidal, brittle, easily powdered,—powder 
iron black ; 8. G. 4:490; scarcely attracted by the magnet. 
Titanic Protoxide, . ‘ ‘ : ‘ 41:1 
Protoxide of Iron, . 3 ; ; A 39°4 
Protoxide of Uranium, : : 3°4 
Silica, . ; ; : : : ; 16°8 
Alumina, or? 
103°9 
“ Abstracting impurities— 
Titanium Protoxide, ; ‘ ; ; 48°8 
Tron Protoxide, : : : 3 : 48-2 
Uranium, : F : ; ' P 4° 
This statement of the presence of arsenic and wranium in such a compound 
induced me to examine “black sands” to a greater extent than I would 
otherwise have done. For the great difficulty of separating them at all 
satisfactorily from commingled siliceous sands, and the doubt which always 
remains as to the presence or absence of ordinary magnetite, made the | 
investigation more or less of a drudgery. I did not qualitatively examine 
many of these black sands,—(though several quantitatively analysed were so 
examined),—but I was quite unable to detect either uranium or arsenic in any ; 
though in several I found traces, larger or smaller, of chromium. 
I hardly think that any one is in a position to pronounce unhesitatingly 
upon the nature of the “iron sands” so frequent upon the shores, and in the 
