THE AOTION OF SEA-WATER UPON CAST-IRON. 151 
Cannon-balls raised at Carlscrona from a sunken vessel, lost fifty 
years previously, were found to be changed through }rd of their 
thickness into a porous graphitic mass, which hecame strongly 
heated when exposed to the air for a quarter of an hour, in f 
80 hot as to drive the water off in steam. (Berzelius Lehrb.) 
Dr. Percy, F.R.S., lately Professor of Metallurgy at the Royal 
School of Mines, in his volume on the metallurgy of iron and steel, 
quotes some instances collected by Henry Wilkinson in his work 
“On the extraordinary effect produced on Cast-iron by the action of 
Sea-water,” 1841. Amongst them he gives the followimg :—“ Many 
of the vessels of the Spanish Armada were sunk off the shore of 
Mull in Scotland, and in 1740 some of the guns of a vessel named 
the ‘Florida’ were raised. These were both brass and cast-iron 
guns, and on scraping the latter which were deeply corroded, they 
a : ose ball 
ave weighed 30 Ibs., were reduced to 19 Ibs, 3 ozs. The S-inch 
¥ 70-Ibs. ones were only 45 Ibs., and although to external appear- 
ance, the same as regular shot, they fell to pieces red hot on 
€xposure to the air.* 
re complete analyses seemed to have been made of the graphite- 
® residues ; hence n comparison could be made between the 
Composition of this specimen from the “Hunter” and that of others. 
Dr. Percy refers to some experiments made by Professor Daniell. 
— of grey cast-iron was acted upon by dilute hydrochloric 
found to consist of a soft spongy substance, but apparently 
peer are beet eres th ere arses 
; Perey’s ‘Tron ” 
+ Poe 5 6 and Steel, igee 147. 5 J ; oF Redinse 
and a <4 uy Steel,” p. 146, quoting from the Journal 
