1825.] 3/;'. ilonfall on Copper SJieu'huig. COl 



the whole of the copper. Whether in short voyages the adhe- 

 sion of" small barnacles is a disadvantage which more than com- 

 pensates this saving, we are ignorant ; but it' so, a smaller 

 (jiiantiii/ of protecting surface must be used ; and the exact 

 proportions for different vessels and voyages will be known after 

 a few experiments. Sir Humphry Davy is still earnestly pur- 

 suing his inquiries on this important subject ; and, we believe, 

 has discovered some new and interesting facts with respect to 

 the conducting powers and electrochemical changes of metals in 

 saline solutions ; which enable him to preserve a considerable 

 portion of the copper without any great consumption of oxidable 

 metal. In the experiments now going on, a nail of zinc or iron 

 is, we believe, placed umler the copper, and in contact with it; 

 and the moist paper upon the wood of the ship in which the nail 

 is placed preserves the electrical circuit with the sea water; so 

 that there is no appearance of protection on the outside, though 

 each sheet of copper has its own protector of r^-— or ^-g- its 

 surface. 



Extract of a Letter from Charles Horsfall, Esq. to Dr. Traill. 



Liverpool, Feh. 19, 1824. 



" The Brig Tickler arrived here from Kingston, in Jamaica, 

 about three weeks ago. She had been out on the voyage from 

 this port to Jamaica and back, not quite five months; previously 

 to her sailing she had been new coppered. Bars of cast iron 

 three inches broad, and one inch thick, covering about 100th 

 part of the surface of the copper, were placed upon each side of 

 the keel from the stem to the stern, and fastened on with copper 

 spike-nails. The Tickler went into the Graving Dock to-day. 

 1 attended before the water had quite left her ; and immediately 

 on the iron on the keel being visible, I went into the dock to 

 examine it. The usual crust of red rust appeared upon it, but 

 on applying a ship's scraper to it, I found the iron quite soft, to 

 the depth of nearly half an inch. A. quantity was scraped off 

 which had all the appearance of black lead, and on handling, it 

 soiled the fingers in the same way that black lead does, and 

 became (jttite hot in the space of a minute or two ; the inner 

 part of the iron bar, or that next the copper, being quite hard. 

 I wrapped a small quantity in |japer, and put it in my pocket ; 

 and on taking it out again, in ai)out a quarter of an hour, it had 

 become very hot, and smoked, and soon assumed the appearance 

 of rusted particles of iron. The bars of iron had been very little 

 reduced in substance during tlic voyage. 



" With respect to the copper, such part of it as was not 

 covered with barnacles appeared bright; and, as far as I couhl 

 judge from such an inspection of it, as perfect and entire as 



