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of a dull blue or gray colour ; and the former was cast when 
the metal was cooler, and consequently not so fluid, but 
rather stiflP, presenting in its fracture a number of small pores 
or air bulbs. 
These comparative circumstances between running castings 
while the metal is hot and fluid, and when it is in a cooler 
and stiffer state, hold good, it will be seen, in other experi- 
ments made with other irons, and they suggest a very im- 
portant consideration, as well for the iron founder as the iron 
master. For it is very probable many unsound castings have 
been made through a want of proper attention to the heat of 
the metal, when run into the moulds. This, of course, is 
attended with loss to the iron founder, and w^ill sometimes 
furnish cause of complaint against the quality of the iron. 
In no case, therefore, should metal be run into the mould 
when it begins to appear cold and stiff. 
In the following experiments all the bars were cast in 
green sand : — 
4. Feb. 24th, 1841 Two bars were cast from No. 3 pig, 
called " Summerlee" Scotch iron, made with the hot blast. 
They each broke with 17 cwt, 2 qrs., presenting in their 
fracture an open grain. 
5. About the same time, two bars were cast from No. 3 
pig, called " Level" Staffordshire iron, which broke with 
16 cwt, each; the grain in their fracture being soft and 
open. 
All the above experiments were made with the ordinary 
No. 3 pig iron, as purchased in the market. We now come 
to experiments made with what is termed and sold for strong 
No. 3 pig iron. 
6. In February, 1841, several bars were cast from the 
Bierley pig, which broke with an average weight of 25 cwt, 
2 qrs, ; the grain of the fracture close and gray ; deflection 
considerable. 
