Brdssl 121 
the author was to ascertain the quantity of alloy the]/ would 
take one with another* 
The first took - 144 grains 
The second - 178 
The third - 200 
The fourth - 208 
The fifth - 230 
The quantity of tinning which copper can take is ex- 
ceedingly variable, and not subject to calculation : the al- 
teration oi the copper by tinning being in all points the 
same, the variations in the weight must necessarily de- 
pend on the more or less exact manner in which the work- 
man removes the superfluous tinning ; and one might be 
induced to believe that the artist has it in his power to 
give a tinning more or less abundant ; but the tinning 
not alloyed with the copper ought not to be considered in 
the same manner as that which is alloyed* The author 
has proved, in general, that good tinning takes a grain df 
tin per square inch* 
Paragraph XL 
On the Duration and Causes of the Destruction of Tin - 
ning* 
Tinning with pure tin has a silver white Colour, and, in 
contact with vapours capable of attacking it, assumes a 
yellowish tint* That made with one-third, one-fourth, or 
one-half of lead, like the old tinning* has more brilliancy^ 
and may be easily distinguished from the former* 
The causes which destroy tinning are friction, calorie., 
and acids 5 the effects of all these causes vary according 
to an infinite number of circumstances, which are deter- 
mined by the author as exactly as possible, and have 
taught him, that, even supposing alloy to be made with 
one-half lead, no individual can swallow per day l-20th 
grain of that metal ; a quantity inappreciable in its effects^ 
You lit Q 
