COMPOSITION OF CAST IRON. 123 
The constant constituents of cold blast cast iron, No. 1, are 
iron, manganese, carbon, silicon, and aluminum., The occa- 
sional constituents are copper, sulphur, calcium, and magne- 
sium. ‘These occur so rarely, and in such minute quantity, that 
we may overlook them altogether. 
The constant constituents occur in the following mean atomic 
proportions :— 
Ber aes ION oS) Sarkis Lie = 77°00 
i atom manganese. . . . ay ay 
4-36 atoms carbon. . ... . = 3:27 
B wee SiCONe ah aire .et/c-,) a == LFOO 
14 aluminum - 1°40—84°42 
If we unite the iron and manganese, and consider them as 
acting the part of basis, to which the carbon, silicon, and alun:i- 
num unite in definite proportions, we have 224 atoms iron and 
manganese; 63 atoms carbon, silicon, and ahupedeitin or 34 
atoms iron and 1 manganese ; 1 atom carbon, silicon, and alumi- 
num. When we compare the different specimens analyzed, we 
observe a considerable difference in the constitution of each. 
In one specimen the iron and manganese were to the carbon, 
silicon, and aluminum, in the proportion of 2-41 atoms of the 
former to I of the latter ; in another specimen as 8°87 to 1. 
Now both of these specimens were from Muirkirk.. These dif- 
ferences doubtless depended partly on the ore, partly on the 
fuel, and partly on the heat employed. They account perfectly 
for the different properties of cast iron. 
But the mean of the whole gives cold blast cast iron, No. 1, com-— 
posed of 33 atoms iron, 1 atom carbon, silicon, and aluminum ; 
and the proportions of these three constituents are very nearly 
4 atoms carbon, 1 atom silicon, and 1 atom aluminum; so that 
the cold blast cast iron of this country consists of 21 atoms 
iron, with a little manganese, 4 atoms carbon, | atom silicon, 1 
atom aluminum. 
2. I examined only one specimen of cast iron, No. 2. It was 
an old specimen, said to have come from Sweden, but I have 
no evidence of the correctness of this statement. Its specific 
gravity was 7°1633 higher than any specimens of cold blast 1 iron, 
No, 1. Its constituents were, 
AGH phir nhs a) baile fe fils y Gad 
Manganese 33. j% Us h%e 2s). «> 1 0°708 
er ONh. ( <.rone ae fens me ae, A OOD 
Bslicom : ( -4Sistielibe osbhisll.. dso wi kiZ6Z 
Peianiinuin °°.) pee ae ote ok te Ose 
Sulphur... - - + 0:038—99°414 
The presence of sulphur i in this specimen leads to the sus- 
