ON THE ACTION OF AIR AND WATER UPON IRON. 225 
It is clear, free from smell, and when first taken up is tolerably 
well tasted, but soon becomes, in a close vessel, unfit for drink- 
ing. A cubic foot of it contains 299 grains of solid matter, 
consisting of 
piipiate Iyer HAG Sie Woe! UW) by: 52°53 
Carbonate lime.-. . . . . , a0*, aga 
POMUOMMe TEN site 88 
Chloride calcium . . . . Ee pi i 2 2 
Chloride magnesium . . . . . . . 4:99 
Chloride sodium . ... ., , mane: ee 
Beas Mert a3 Criteria ries ii) RSI 13 
100°00 
It gives uncertain traces of a free alkali, probably carbonate of 
soda, derived in all probability from the beds of albite, over 
which the river Liffey passes, a fact long previously noticed by 
my friend Dr. Apjohn. The boiling-point of this water-is 
214° Fahr. in glass, barom. = 30°15 inches. Its specific gravity 
is = 1001-39; its saline contents vary very slightly between 
winter and summer. 
151. All the waters in which the various classes of iron ex- 
perimented on have been immersed are now described ; and as 
the methods by which these experiments have been conducted, 
the particular objects in view and the precautions observed have 
been detailed in my previous report*, it will only be further ne- 
_ cessary to premise that— 
152. The corrosive action of air and water in the above con- 
ditions upon iron presents its effects in five characteristic states 
of oxidation or rust, on the surface of the metal varying with 
the nature of the cast iron, the mode of casting, &c. &c. These 
are referred to in column 13 of the tables of results, the nomen- 
clature of which it may be necessary to explain. 
It is unchangeable in all the tables, and embraces the follow- 
ing terms, which are thus explained. Ist, Uniform, or when 
the whole surface of the iron is found covered uniformly with 
@ coat of rust requiring to be scraped off, and leaving a smooth 
‘Ted surface after it 3 2nd, Uniform P., or uniform with plum- 
bago, where the surface, as before, uniformly corroded on 
Scraping is found in some places covered with plumbaginous 
Matter}, and leaving a “ piebald”’ surface of red and black after 
it; 3rd, Local, where the surface of the iron is found only rusted 
im some places, and free or nearly free from rust in others ; 
4th, Local Pitted, where the surface is found as in the last 
* Report, § 68 to 84. '  $ Report, § 20. 
1840. Q 
