4A REPORT—1863. 
Again, Mr. W. Baker (of Sheffield) informs me that just the converse takes 
place with lead; for the purer the lead the larger the crystals. Now, these 
facts being known, it seemed possible that in alloying some metals with traces 
of others, either the crystalline form of the alloy might be altered or the 
tendency to crystallize increased or decreased, and thus cause the great change 
in the conducting-power. This supposition is, however, proved wrong by the 
following experiments* :— 
I. If to melted tin traces of lead or bismuth be added, a decrement in the 
conducting-power is observed which increases with each successive addition of 
metal. 
II. If to melted lead traces of tin be added, an increment in the conducting- 
power is observed ; if, on the contrary, bismuth be added, a decrement. 
IIL. Ifto melted bismuth traces of tin or lead be added, a decrement ; but on 
further addition, an increment in the conducting-power will be observed. This 
behaviour corresponds with that of these metals in the solid state ; in fact, if 
the conducting-powers of a series of these alloys in a liquid state were deter- 
mined, the curve representing them would in all probability be similar to 
that of the alloys in a solid state. 
The explanation which I would offer of the cause of this behaviour is as 
follows :— 
Let it be assumed that the metals belonging to Class B, when they are 
alloyed either with one another or with one of Class A, undergo a change (in 
other words, are converted into an allotropic modification), and that this change 
is brought about by a small quantity of the other metal, the quantity of the 
metal required to complete the conversion being dependent on the metal em- 
ployed. With the help of this hypothesis, we are able to explain many of the 
phenomena which occur when making the alloys, as well as the reason of the 
marked change in most of the physical aig oa of some metals when alloyed 
with traces of another. 
A few examples will show this clearly. Take, for instance, the case of the 
zine-copper alloys, the curve representing the conducting-power of these 
alloys has the same form as those of the other alloys belonging to this group, 
and the percentage decrement in their conducting-power between 0° and 100° 
is exactly that which would have been deduced from the law which regulates 
this property. From these results it may be deduced that solid alloys of zine 
and copper are only solidified solutions of zinc and of an allotropic modifica- 
tion of copper in one another. 
Some experimenters have expressed their opinion that there exist chemical 
compounds in these alloys; and they base their supposition on the following 
facts :— 
I. When zinc is added to copper in the melted state, a great evolution of 
heat is observed. 
II. That some of the zinc-copper alloys crystallize more readily than others. 
Storer,in his paper? “On theCopper-zinc Alloys,” states, “It is awell-known 
fact that the combination of copper with zinc is attended with ebullition of 
considerable violence, so that portions of the melted mass are often thrown to 
a distance of several feet from the crucible. Yet it does not appear to have 
been previously noticed by chemists that this action is much more energetic 
while the first portions of zinc are being added to the copper, and that the 
loss of zinc by volatilization is far greater at this time than at any subsequent 
stage of the operation.” This fact may be explained by assuming that the specific 
heat of the allotropic modification of copper is less than that of copper in its 
* Matthiessen and Vogt, Phil. Mag., March 1862, 
+ Memoirs of the American Academy, vol. viii. p. 26. 
