^1825.] Coppe?' Sheathing. 17 



keel by erow spikes. It covered about ■^^'o-of the surface of her 

 copper. Since that period she has made two voyages to De- 

 merara, and was, at the conclusion of the last, put into a grav- 

 ing dock, when her copper was found perfectly free from 

 corrosion, and there were scarcely any substances adhering to 

 it, except a very few minute barnacles, near the keel fore and 

 aft. This case shows that over defence was not the cause of the 

 foulness of the bottom of the Tickler; for both in this vessel 

 and in the Huskisson, the proportion of iron to the copper was 

 greater than in that ship. The iron spikes employed to fasten 

 the iron on the keel of the Dee, were so much corroded, as to 

 endanger the falling off of the bars; copper nails are, therefore, 

 to be preferred. 



The Dorothy. — Dr. Traill states, that the following particulars 

 of the Dorothy's outfit and return, were communicated to him 

 by his intelligent friend Mr. Horsfall, one of the owners of the 

 ship in.the beginning of May : — 



" The Dorothy had been coppered about a year, and had made 

 one voyage to Bombay and back to this port, when in May, 

 1824, it was determined to place bars of iron four inches broad, 

 and one inch thick, along her keel, covering about y^ part of the 

 copper, in the expectation that the iron would at least so far 

 preserve the copper from corrosion that it might be permitted to 

 run a second voyage to India without being renewed, which can 

 seldom be done with perfect safety. The iron extended from 

 on^end of the keel to the other, and was fastened on with copper 

 nails with large heads. The Dorothy thus defended sailed 

 again for Bombay in June, and returned to Liverpool about a 

 month since. She was put into the graving dock yesterday 

 (May 3), and an examination of her bottom took place as soon 

 as the water had left her. 



" The copper appeared no more reduced than at. the termina- 

 tion of the first voyage. The iron was diminished generally 

 about f inch in breadth, and from ^ to -i an inch in thickness. 

 At the ends of the vessel, for about two or three feet, the iron 

 was much more reduced than at any other part. It was covered 

 with the usual rust, not at all resembling cast iron, under similar 

 circumstances. The flat of the ships' bottom, from end to end, 

 and from six to eight feet in breadth, was full oi fleshy barnacles 

 (lepas anatifera) of uncommon length, and a few of the large hard 

 shell species (balanus tintinnabulum).*" 



What remains of the iron is still considered a sufficient pro- 

 tection for a third voyage to India, and " it appears only to be 

 necessary to drive the large copper nails up a little to secure the 

 iron bars for the next voyage." 



Note by Dr. Traill. — We remarked that the specimens of the 



♦ Sulphuric acid wtsused to loosen and detach the shells; :•' '] • ^ '( ' '^ 

 New Series, vol. x. c 



