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POPULAR SCIENCE REVIEW. 
without difficulty. To ensure success, the greatest care must be taken that 
no charcoal or other solid carbon comes into contact with the points to be 
welded, as otherwise phosphide of copper would be formed, which would 
cover the surface of the copper, and effectually prevent a weld. In this 
case it is only by careful treatment in an oxidising fire and plentiful appli- 
cation of the welding powder that the copper can again be welded. It is, 
therefore, advisable to heat the copper in a gas flame. As copper is a much 
softer metal than iron — it is much softer at the required heat than the latter 
at its welding heat — it must be carefully hammered with a very light 
hammer, or better, by a mallet, and so shaped as to resist the blows as far as 
possible. — Vide Mining Journal, May 15. 
The Minerals of the Breitenhach Meteorite . — The Proceedings of the Royal 
Society for May contain a report of Professor Maskelyne on this subject. 
This meteorite, which belongs to the rare class intermediate between meteoric 
irons or siderites and meteoric stones or aerolites (a class to which I applied 
some years since the term siderolites), was found in Breitenhach, in Bohemia. 
It is a spongy metallic mass, very similar to the siderolite of Bittersgriin, in 
Saxony, the hollows in the iron being filled by a mixture of crystalline 
minerals. These minerals seem to consist almost entirely of two 5 and the 
present notice deals with these two minerals. 1. One of them is of a pale 
green colour, crystallising in the prismatic system, and presenting at once 
the formula of an augitic mineral and a crystalline form nearly approximat- 
ing to that of olivine. 2. The other mineral is one of very great interest. 
It is, in short, silica crystallised as tridymite. In bulk it forms about a third 
part of the mixed crystalline mass. The crystals are very imperfect 5 but 
measurements in those zones accord with those of an hexagonal crystal. A 
section made for examination in the microscope showed two small crystals 
in which the axis happened to be normal to the section. Light traverses 
these crystals wfith equal brilliancy during the rotation of the crystal be- 
tween crossed Nicol prisms. That this was due to gyratory polarisation, 
and of a right-handed kind, was shown in the following manner : — A com- 
parative experiment was made with two sections of quartz of opposite 
qualities, and of the requisite thickness to give the sensitive tint” with 
crossed Nicols ; and below these were placed two thin sections of right and 
left gj'rating quartz, giving an orange tint. The two minute microscopic 
sections gave, on comparison of the colours in the centre of the field in each 
case, unmistakable evidence that the gyration was similar to that of ^‘right- 
handed” quartz. Tliere can be no doubt from these results, further details 
of which are to be laid before the society, that this mineral is silica in the 
form of its opaloid crystal, to w'hich Von Bath has given the name of 
Tridymite. 
Ik'tedion of Phosphorus in Cast Iron. — !M. Tanten, n French metallurgist, 
who has given mucli attention to this important problem, makes the follow- 
ing remarks: — It is w^ell known that very small quantities of phosphorus 
produce no sensible alteration in the quality of cast iron, whereas if the pro- 
portion exceeds a few thousnndth parts tlie iron is robbed of its most essential 
(jualities. It is very important, tlierefore, to a.scertaiii the exact amount of 
])hosphorus present. Nearly all the methods in use for this pui^pose consist 
in treating the iron by means of oxidising agents, so as to cause the phos- 
