656 EXPERIMENTAL INVESTIGATION OF THE 
magnet, instead of testing them in the usual way 
by means of a delicate magnetic needle. And if 
this test be accurately performed when the metal 
first arrives from the foundry, the detection of 
any concealed magnetism, even if very feeble, 
will be almost certain ; and much of that labour 
and uncertainty, which must always attend exami- 
nations by the needle, would be avoided. Unfor- 
tunately, however, too much reliance is usually 
placed on the mere appearance of the brass, or on 
the character of the foundry whence it is procured, 
and the consequence is, that but very few brass 
compass boxes that are in common use are 
entirely free from magnetic action. 
42. The next alloy of importance that I have 
examined is German silver, in which nickel is 
one of the principal constituents. In the best kind 
of German silver, (constituted of copper eight 
parts, nickel six, and zinc three), a slight magnetic 
action has been detected, but in the inferior kinds 
of German silver, into which only about three 
parts of nickel enter, I have not detected any 
magnetic action whatever. Hence the magnetism 
of that portion of nickel is obviously neutralized 
m that particular alloy. 
