34 ON THE ALLOYS OF COPPER AND ZINC, 
which shoot out from the points at which the alloy comes in contact with the 
cold metal of the mould. In the instances which have fallen under my notice, 
the ingots being from an inch to an inch and a half in depth, the fibres have 
shot up three quarters of an inch, or more, from the bottom of the ingot, leaving 
only a sheet of metal about a quarter of an inch in thickness on top, which had 
cooled more slowly by contact with the air. 
Fig. 3, a, represents in section a frag- 
ment of one of these ingots. One side— 
d seen at the right — as well as the bottom 
Y of the portion figured having been in direct 
| contact with the iron mould in which the 
ingot was cast, the crust just alluded to 
may also be seen above the fibres: On 
removing portions of this upper layer, its 
Fig. 8. inferior surface will be found studded with 
crystals, often of great beauty, — Fig. 3, c conveys but an imperfect idea of a portion 
of one of these, — while others frequently occur impacted among the fibres themselves. 
Indeed, these fibres, although described by Calvert and R. Johnson * as prismatic 
crystals, indicating that the alloy Cu Zn is a definite chemical compound, are evidently 
nothing more than collections of octohedral crystals, similar to those which form 
the fibres of sublimed sal-ammoniac and of several metals.+ 
By comparing the striations on these fibres with those upon any of the crystals 
of the series, it is impossible to resist the conviction that the former are mere 
aggregations. This conclusion is confirmed by the fact that the individual crystals 
which have been just mentioned as occurring above and among the fibres are evidently 
parts of the same system as the latter. Fig. 3, b represents a portion of one of 
the fibres somewhat magnified. It often happens that this alloy, known as brazier's 
solder, is run into cylindrical moulds of two or three inches in diameter, pierced 
in earth; in this case the fibres shoot out from all sides towards the centre, leaving 
at the middle of the bar a sort of neutral ground in which tolerably well-formed 
crystals frequently occur. The solder is prepared for market by warming it slightly, + 
* Journal of the Franklin Institute, (3.) XXXVIL 200. See also Philosophical Transactions, Vol. 
CXLVIII. p. 367. 
+ Vid. Savart, Annales de Chimie et de Physique, (2) XLI. 65. 
1 It must not be heated above a very moderate temperature, for, like metallic zinc at certain temperatures, 
it then becomes somewhat tenacious or pasty, and cannot be powdered. 
