190 Scientific Intelligence. — Mineralogy. 
precipitated by sulphuric acid, the operation being conducted at 
a boiling temperature, to prevent the precipitation of any sele- 
niate of lead. The filtered solution was then concentrated by 
evaporation, and selenium thrown down by sulphate of ammonia 
and sulphurous acid. The cobalt was next separated by the 
hydrosulphuret of ammonia. The proportion, as drawn from 
the mean of three nearly corresponding analyses, is, 
Lead, . . , 70.98 
Cobalt, ... 0.83 
Selenium, . . 28.11 
99,92 
With respect to the atomic constitution of this ore, Professor 
Stromeyer remarks, that “ its constituents are combined precise- 
ly in the proportion of their equivalents, and the quantity of the 
selenium corresponds not only to the lead, but also to the cobalt, 
and that, therefore, both metals are to be regarded as in combina- 
tion with selenium. The seleniate of lead, too, agrees with 
the sulphuret of that metal in this respect, that, when both its 
constituents are oxidised, the selenic acid and oxide of lead are 
in the precise proportion to form a neutral seleniate of lead, just 
as the oxidation of galena gives rise to a neutral sulphate of 
lead. The discovery of such a compound is therefore to be an- 
ticipated whenever a native seleniuret of lead exists.” I take 
this opportunity to mention, that the native sulphuret of selenium 
which Professor Stromeyer detected among the volcanic products 
of the Lipari Isles, of which I communicated a short notice some 
months since, was found among a mixed sublimed mass of muri- 
ate of ammonia and sulphur. It was disposed in layers, and, 
from its brownish yellow colour, gives rise to the supposition 
that the muriate of ammonia at such parts contained iron. A 
superficial examination proved, however, that no iron was pre - 
sent, and this observation led to the detection of the selenium. 
In a letter which I have just received from Professor Stromeyer, 
he informs me that another ore has been found in the Hartz, 
containing the seleniurets of lead, copper, silver, and mercury, 
with the examination of which he is at present occupied”.— Let- 
ter from Dr Turner. 
10. Sulphato-tricarbonate of Lead . — Our friend, Dr Ander- 
son of Leith, some time ago sent to Stromeyer, the distinguish- 
