ON THE ACTION OF AIR AND WATER UPON IRON. 247 
actual union, or, as I shall call it, 2 metallic contact, as in the 
case of zinked iron, or iron coated with zinc at its fusing 
temperature. Hence there have been made eight distinct trains 
of experiment on this one branch of the subject, each of which 
has been carried on upon cast iron, upon wrought iron, and 
upon steel, as the following scheme will serve to indicate : 
All freely exposed to air and carbonic acid. 
Tn sea water. 
In fresh water. 
In sea water. 
In fresh water. 
Tn sea water. 
In fresh water. 
In sea water. 
In fresh water. 
In sea water. 
In fresh water, 
In sea water. 
In fresh water. 
In sea water. 
In fresh water. 
In sea water. 
In fresh water. 
In sea water. 
In fresh water. 
In sea water. 
Submerged 12 inches ......... 
Cast iron 
and 
zinc. 
In simple contact.. 
Submersion indefinitely stall { 
Submersion 12 inches ......... 
In metallic contact. 
Submersion indefinitely small { 
Submersion 12 inches ......... 
In simple contact.. 
Wrought SGA indefinitely small 
iron and 
zine. Submersion 12 inches ......... 
In metallic contact | 
Submersion indefinitely small { 
Submersion 12 inches ......... 
In simple contact.. 
Cast steel Submersion indefinitely small ipa 
and 4 n fresh water. 
zinc, Submersion 12 inches ......... obs Vier 
In fresh water. 
Jn sea water, 
In metallic contac | 
In fresh water. 
Submersion indefinitely small { 
I will not venture to enter here upon the lengthened detail of 
these experiments, which will probably appear in a more suitable 
place, but merely state the method and principal results ar- 
rived at. 
206. The fresh water used in all these experiments was that 
which supplies the city of Dublin at the north side; it comes 
from Lough Ouwell, ina limestone district, county Westmeath ; 
it contains no solid matter when filtered, but a trace of car- 
bonate of lime and of carbonate of iron. It holds in combina- 
tion, however, one volume in eight of gases evolved on boiling, 
which consist of 
umtospheric air J ers PY Fo olgasy 
Ramee cic, .4) OYERMUEE Ae I See MOTE a ee) 
100°0 cubic inches. 
The sea water used was invariably that from Kingstown Har- 
bour, of which the analysis has been already given. 
