SCIENTIEIC SIJMMAEY. 
251 
matter suj)puratecl containecl a lilac colouring matter allied to indigo, lias 
been recorded by Dr. lY. B. Herapath. A microscopic examination of the 
liquid showed the absence of fungi, and from the circumstance that when 
placed in a closed bottle the liquid lost colour, and regained it on exposure 
to air, it was eiddent that some change of oxydation was undergone. Tliis 
led the Doctor to chemically examine the pus ; and, upon treating it with a 
solution of hypochloride of lime, the colour was as quickly discharged as if 
indigo had been present. From this Dr. Herapath concludes that either 
indigo or some substance allied to it was absolutely present in the system of 
the patient. — Yide The Chemical News, October 8th. 
METALLUKGY AND MINING. 
Extraction of Auriferous Silver in the Liquid Way. — Hitherto the difficulty 
in extracting alloys of gold and silver from ores by the wet method has been 
the complete separation of the two. This, however, may now be achieved 
by washing and lixiviating the ore with a concentrated solution of common 
salt saturated with chlorine, by which both metals vfill be smiultaneously 
precipitated. — Yide Mining and Smelting Magazine, October. 
Preservation of Iron in Water. — At a late sitting of the Academy of 
Sciences M. Becquerel read a jiaper on the preservation of cast-uron and iron 
in fresh-water. He had previously shown that when a plate of either 
material was in contact with a zinc plate, not exceeding the hundredth part 
of the surface of the former, the intensity of the derived electrical currents on 
the protected metal (iron) would in sea- water diminish as the distance from 
the pomt of contact of the two metals increased ; but nevertheless so that 
the protection afforded by these derived currents would still extend to a 
considerable distance from the said point of contact. In fresh-water there 
are fewer divided currents on the ' surface of the metal, a fact which M. 
Becquerel attributes to the difference of conductibility of the two liquids, and 
the degi'ee of chemical action which each exercises on the zinc, since these 
two circumstances tend both to increase the intensity of the current. 
M. Becquerel asserts that a pile of 9,837 cannon balls, twelve centimetres in 
diameter, may be protected from oxydation under water by surrounding it 
with zinc bands having an aggregate surface of two square metres. — ^Yide 
Comptes Eendus, October 31st. 
The Cementation of Iron. — The controversy upon this subject is still continued 
by M. Caron on the one side and M. Margueritte on the other ; the former 
having laid down the theory that in cementation on a large scale iron is 
always brought into contact with cyanides, which alone possess the power of 
cementing ; the latter endeavourmg to prove, on the contrary, that kon may 
be converted into steel by j)ure carbon (that is, by either diamond, carbonized 
sugar, or plumbago), or else by pure carbonic oxide. — Yide The Artizan, 
December. 
Copper in Spain has recently been discovered by M. Tribaut, a French 
mining engineer. This gentleman has found a very rich vein of cobaltiferous 
copper, containing nearly nine per cent, of oxide of cobalt, near Oviedo, in 
Spain. We learn that he has entered into an agreement with an English 
house to take nearly the whole produce of his mines. 
