28 



MR. E. W. BINNEY ON THE ACTION OF 



some cases reaching to one or two hundred yards of a column, 

 against the sides of the tubbing. Now, should the iron from 

 any cause give way, great loss of life must necessarily ensue ; 

 for that material generally gives but little warning of its 

 breaking, and the irruption of water into the pit before the 

 miners could escape, must therefore prove most disastrous, 

 especially in deep collieries, where there are often but two 

 shafts, and those placed close together. 



Mr. Robert Mallet, M. I. C. E., &c., in his valuable reports 

 (published in the 8th and 13th volumes of the Transactions of 

 the British Association for the advancement of Science) upon 

 the action of air and water, whether fresh or salt, clear or 

 foul, and of various temperatures, upon cast iron, wrought 

 iron, and steel, gives many instances of the effects of acid 

 solutions and sea and fresh water upon these metals. 



The action of sea water and a mixture of salt and fresh 

 waters upon cast iron, by converting it into what has been 

 called plumbago, is well known, and many instances have been 

 recorded of iron guns and shot having been partially con- 

 verted into that substance. The guns of the Royal George 

 at Spithead may, amongst mony others, be mentioned as a 

 case which has lately come before the public. So certainly is 

 this effect produced, that it strongly behoves those who have 

 charge of the lighthouses now so often erected in the sea 

 upon cast iron pillars, carefully and frequently to inspect such 

 structures, for day by day their supports must be weakened 

 by the action of the salt water. 



With regard to the effect of sea water upon wrought iron, 

 there appears to be some difference of opinion, for Mr. Mallet* 

 states that he has in his possession a portion of an ancient 

 anchor taken up in tlie port of Liverpool, the iron that re- 

 mained of which was of remarkable purity, and which was 

 converted into plumbago of unusual hardness and brilliancy 

 to the depth of half an inch. This plumbago did not heat on 

 * Vol. vii. Brit. As8. Rep., p. 259. 



