824 
T/te Manufacture of Iron in 
recent origin, singularly deficient in phosphoric compounds. The 
Labour Commissioner of the United States gives certain particulars 
respecting some 100 specimens of ore. Of these thirty-five average 
65‘43 per cent, of metallic iron, which, if all were per-oxidised, leaves 
only 6 '53 per cent, of foreign matter. If all these were the produce 
of the Lake Superior mines — and most of them doubtless are so — we 
may, from the hardness of the older rocks in which they occur, 
expect only a small admixture of earthy contamination. These ores, 
therefore, belong to strata of the Silurian age, a period when phos- 
phoric acid had not become concentrated to the extent in which it 
is found in more recent geological horizons. Accordingly, we only 
have 0-061 per cent, of phospliorus in these thirty-five cases. The 
next group of ten varieties of ore gives an average of 57 ‘8 per cent, 
of iron, and therefore 17’43 per cent, of earths, and 0-222 of phos- 
phorus. AVe then come to twenty-six specimens of much more recent 
origin, and containing only 45-61 per cent, of iron, 34-15 of earths, 
and 0-339 per cent, of phosphoric acid. Lastly, seven examples, 
chiefly of the coal formation, with 35-46 per cent, of iron, 35-46 of 
earths (49-37 inclusive of carbonic acid), and 0-474 percent, of phos- 
phoric acid. 
In order to extend the field of observation I have taken out of a 
list of analyses in Percy’s work on “ Iron and Steel ” the follow- 
ing English examples, which I have placed according to their geo- 
logical sequence, beginning with the oldest : — 
Descriptiou of the Ore 
Geological Position 
Number 
of 
Examples 
Average of 
Phosphoric 
Acid 
Average 
of 
Iron 
Red hematite . 
Probably Carbon- 
iferous Limestone 
() 
per cent. 
Trace 
per cent. 
(5 4-89 
South Wales . 
Coal formation 
10 
0-151 
28-42 
West Yorkshire 
Coal formation 
(> 
0-189 
32-OS 
South Staffordshire 
Coal formation 
ordinary run 
10 
0-201 
37-82 
Derbyshire 
Coal formation 
0 
0-204 
29-15 
Most likely North 
Yorkshire 
Lias 
3 
0-542 
38-95 
In thus tabulating tlie ores of iron to show a possibility of their 
content of phosphorus having increased as the concentration of this 
element by vegetation progressed, I would not be understood as main- 
taining that there are not exceptions to such a supposed law. On the 
contrary, I am fully aware that exceptions are to be found to its ope- 
rations, one indeed appearing in the table of examples just quoted. 
In it, among British ores at the head of the list, comparatively 
free from phosphorus, stands red hematite, found so abundantly 
in a formation so recent as the Carboniferous Limestone, and in the 
adjoining rocks. 
From whatever cause, it is quite certain, however, that the clay 
ironstones of the Carboniferous strata are so charged with phosphoric 
