IEA I 
ra eo 
desea ame 
COMPOSITION OF CAST IRON. 125 
Clyde. Carron. | Carron. Clyde. Clyde. 
Tron -cecccccseeces 97:096 | 95°422 | 96°09 94:966 | 94:345 
Manganese......... 0°332 | 0336 | 0-41 0160 | 3120 
ATDON seeseeeeeees 2°460 2:400 2:48 1560 1°416 
Silicon .sseesseeeee 0:280 1820 1:49 1322 0°520 
Aluminum ......... 0°385 0°488 0°26 1374 0°599 
Magnesium......+.. — —_— — 0°792 | —— 
ns | ce | | | 
100°55 | 100-466 |100°73 | 100°174 | 100: 
The mean of these analyses gives us, 
Atoms. 
Dri)! ee we 9584 or 27-31 bes 
Manganese . . O°87lor 0°249 
Carbon. .*.. © 2°099 or 2°79 
Silicon. . . . 1°0860r 1°086 -1 
Aluminum . . 0°422o0r 0°337 
101°285 
Or, in the proportion of 6% atoms of iron and manganese to 1 
atom of carbon, silicon, and aluminum. In the cold blast cast 
iron, we have, Iron. Carbon, &c. 
InNo.l ... . . 3} atoms I atom. 
Bran Nos Bodh). yen ce oe AE i 
In hot blast . . . . 63 1— 
Thus it appears that when iron is smelted by the hot blast its 
specific gravity is increased, and it contains a greater proportion 
of iron, and a smaller proportion of carbon, silicon, and alumi- 
num than when smelted by the cold blast. 
The atoms of carbon, silicon, and aluminum are to each other 
nearly in the proportions of 12, 5,and2; so that the proportion 
of silicon compared with the carbon is nearly twice as great in 
the hot blast iron as in the cold blast. 
These are consequences that might have been anticipated from 
the theory of the process, as I have explained it in a preceding 
part of this paper. 
As to the qualities of the two kinds of iron I do not consider 
my experiments as calculated to enable us to draw any conse- 
quence of much importance. Hot blast iron is obviously purer 
than cold blastiron. It is said by several of the Glasgow steam 
_ engine makers whom I have consulted on the subject, that the 
_ iron by the hot blast is not so tough as that made by the cold 
_ blast ; and one very extensive house in Glasgow, in order to ob- 
_Viate this objection, is in the habit of adding a little Welsh iron 
to the hot blast iron before casting, and this I have been assured 
by the manager of the works obviates the defects. 
