1843.] on the effects of Sea-water on Iron. 1075 



P.S. — While using the above composition, the pounding of it should 

 not cease, otherwise the substance will become hard. 

 (True Copy.) 



(Signed) C. E. Greenlaw, Secretary. 

 Fort William, Marine Superintendents 

 Office, the 23d Sept. 1843. 



To Dr. O'Shaughnessy, Medical College. 



20th May. 



My dear Sir,— I have been engaged for sometime at home in ob- 

 taining information as to the best means of preventing corrosion of Iron 

 Sea-going Vessels, and had contracted to build an iron opium clipper, 

 but waited to see the effect of the barnacle and limpet on the iron 

 sides in three voyages from Liverpool to the Brazils. On docking her 

 on her first return, you could not put the palm of the hand on her 

 bottom clear of a limpet. On the second return, I could not find room 

 for the ball of my thumb, so completely covered was it. The first 

 voyage she was painted with red lead and linseed oil, the second some 

 white lead was added, and the third voyage she was offered for sale in 

 consequence of the inability to keep the bottom from getting so very 

 foul, as to reduce her sailing qualities far below a common merchant 

 ship, though she was a fast vessel. 



The Leviathan Steamer, 2700 tons, building at Bristol, I visited, 

 and saw experiments being made with 8 or 10 different compositions. 

 The builder told me they had tried near 40, and I dare say by this time 

 something will have been discovered. 



I am a member of the institution of Civil Engineers, and will write 

 to the Secretary next mail, to ascertain what has been done or discover- 

 ed, and inform you of the result. 



As to the copper, it had a bar of iron along the keel, and up and 

 down stern and stern-posts. We had it on our voyage to China. The 

 iron was destroyed in two years, I think, and I never renewed it. The 

 copper lasted eleven years ; with exception of her voyage to China and 

 to Suez, she was running in the Hooghly. The patent yellow metal, or 

 Muntz's patent, much used now for shipping, being about 20 per cent. 



