Second Report upon the Action of Air and Water, whether 
fresh or salt, clear or foul, and at various temperatures, 
upon Cast Iron, Wrought Iron, and Steel. By Roserr 
Mauer, M.R.I.A., Ass. Ins. C. E, 
140. Since my former report upon this subject was submitted 
to the British Association, as now printed in its Transactions, 
additional interest and importance has been given to every 
branch of the inquiry, as to the durability of iron under its 
various circumstances and conditions, by the rapidly-increasing 
introduction of iron vessels to navigation in the most difficult 
and lengthened voyages. 
Amongst the several problems of a strictly scientific cha- 
racter requiring solution before the use of iron ships for distant 
voyages, or their economic adoption, under any circumstances, 
can be pronounced ¢ertain, is the great question of their dura- 
bility as compared with those of timber; and it is hoped 
that the experiments made or in progress under the auspices 
of this Association, and about to be detailed, will render, in 
part at least, a satisfactory reply thereto. But, besides the 
desirableness of prolonging the existence of iron ships, it is 
of the utmost importance to prevent the formation of rust at 
all upon them under water, which, once produced, affords a 
*nidus’’ for the growth of marine animals and plants by which 
the ship’s bottom is rendered foul, and her sailing qualities are 
greatly interfered with. These causes of foulness are found to 
adhere with the utmost obstinacy to the oxidized iron. It is 
part of our object to endeavour to find remedies for these 
evils. 
141. The present report contains the first set of tabulated 
results which I have obtained as to the amount and nature of 
corrosion of cast and wrought iron under several different con- 
ditions of exposure to the chemical action of air and water, 
whether of the ocean or of rivers, &c. And as this subject 
essentially consists of two distinct parts, or is to be viewed in 
two different lights, namely, as a chemical or purely scientific 
inquiry, and as a technical one, from which useful practical 
results are to be derived, and as some portions of it, viewed in 
the former light, are still under experiment, and likely to be so 
for some time to come, I purpose, on this occasion, to reserve 
the purely scientific consideration of the subject, as far as pos- 
