174 
DE. A. MATTHEESSEX OX THE ELECTEIC 
tures but solutions of one metal in the other, may be deduced from the fact of their 
fusing-points being generally lower than the mean of that of the volumes taken. 
Secondly. To what is the rapid decrement of the conducting power due ? 
The only answer which I can at present give to this question, is that most of the 
other physical properties of the metal are altered in a like manner ; for on looking at 
the alloys made with the metals of Class A. with one another, we see that most of their 
other physical properties are not at all altered ; for amongst them, for instance, we hnd 
no brittle ones ; they appear, in fact, to take an equal share of the properties of the 
metals composing them. But now let us examine the alloys of the second class, and 
we immediately discover great differences ; alloy gold, the most ductile of all metals, 
with small per-centages of tin, lead, or zinc, and it becomes as brittle as glass. Again, 
alloy silver with small per-centages of the above metals, and its properties are much 
altered. Silver, which, when pure, is one of the easiest metals to draw, when alloyed 
with more than 3 per cent, of tin and 2 per cent, of lead, becomes so brittle, and its 
tenacity so much impaired, that it cannot be drawn. I do not mean to say it is impo>- 
sible to do so, but it was tried several times udthout success. On the other hand, we 
do not find any marked differences in the ductihty, hardness, See. of tin or lead v^ hen 
alloyed with silver; we may add 10, nay even 20 per cent, of silver to them, and the-} 
remain ductile, and may be pressed into ivire without any trouble. Of course, with lead 
and tin alloyed with small quantities of gold, the case is somewhat different, as we have 
here chemical combinations coming into play ; nevertheless, we may add to them 5 per 
cent, of gold without altering their ductility, &c. to any great extent. Bismuth alloyed 
with lead or tin becomes more brittle, and in wme its tenacity is impaired ; but tin and 
lead alloyed with large per-centages of bismuth, always retain a considerable amount of 
ductility, &c. 
Again, take the alloys of the third class. Although amongst the gold-silver and the 
gold-copper alloys we find no brittle ones, yet we know how hard gold, sdver. and copper 
become when we alloy them with small quantities of other metals, and that they lose 
more in proportion of their ductility, &c., by the addition of small than of large quan- 
tities of strange metal. 
From these facts, we need not be surprised at the rapid decrement of the conducting 
powers of the metals belonging to Class B, when alloyed with any other metal : tor 
when we find most of their other physical properties more or less greatly altered ly. 
traces of foreign metals, might w^e not also have expected this result I For where ws. 
see no marked change in most of the other physical properties ot alloys, as in tlie first 
class and in the second, on the one side of the curve, there we have nearly their calcu- 
lated conducting powers. 
It would be very interesting to determine quantitatively some ot the other physical 
properties of the alloys, to see whether in them these properties will decrease in the 
same marked manner as the conducting powers, when a metal belonging to Class B. is 
alloyed with any other metal. I intend therefore to commence, especially with this 
