ON JEWS’ TIN. 83 
I think the subject of Cobalt in Tin Ores is worthy the atten- 
tion of those who are more particularly interested in the Smelting 
of Tin; and I see no reason why the Cobalt should not be ex- 
tracted profitably from the Hard Head, and at the same time afford 
a ready means for the recovery of a large portion of the Tin it 
contains, and which is now lost. 
XV.—WNote on a portion of the incrusted surface of « block of “ Jews’ 
Tin.” —By J. H. Couns, F.G.8., Secretary of the Royal Corn- 
wall Polytechme Society. 
ie the last meeting of the Royal Institution of Cornwall, a 
A. block of “Jews’ Tin” from Tremethack Moor, in Madron, 
just purchased for the Institution, was exhibited for the first time 
to the members. This block was partially covered with a hard 
and brittle brown coating, in some places as much as 4 inch thick. 
Mr. W. Jory Henwood, F.R.S., the late President, before the 
expiration of his term of office, placed a portion of this coating 
in my hands for analysis. 
The brown color was not evenly distributed—some parts being 
darker than others; and under the microscope several minute 
shining particles were visible—probably particles of Metallic Tin. 
The specific gravity of the substance was 5-64. 
After a few preliminary trials I found I had just 48 grains 
at my disposal, which I had previously reduced to a fine powder. 
On drying this powder, at a temperature of 120° C, it was reduced 
to 45 grains. 
The powder was boiled with distilled water for a time, and 
yielded a solution from which I obtained ‘5 gr. of Tin and °3 gr. 
of Chlorine='8 gr. of Sn Cl,. 
