TRANSACTIONS OF THE SECTIONS. 45 



The copper from the Plover and from the Jane, near the water-line, which was spotted 

 with uniform punctures in the shape of a horse-shoe, with a trail running invariably 

 in the direction of the wash, looked as if damaged by organic action. The specimens 

 were shown on the table. This appearance did not descend below the reach of air 

 or froth. 



To examine the question of increased corrosive power in tropical waters, Mr. Owen 

 undertook to obtain samples from the Gulf-stream and other points ; as well as from 

 Falmouth harbour, where the packets are moored. Meanwhile appeared Professor 

 Daniell's announcement of the large quantities of sulphuretted hydrogen in the 

 waters of the Guinea coast. 



The samples were collected and ticketed with due care : four from the Gulf-stream, 

 one including the weed ; two from the Caribbean Sea off Barbadoes ; one from Fal- 

 mouth harbour. No. 4, with the weed, was nearly saturated with sulphuretted hy- 

 drogen, the others inodorous. Neither of them reddened blue litmus paper, but all 

 slightly aflFected red litmus paper. No. 4. blueing it distinctly. None but No. 4. 

 affected sugar of lead paper. In specific gravity they were nearly alike— the Gulf 

 and Caribbean waters, 10283 ; the Falmouth and Plymouth waters, 1027-4. They 

 all required nearly the same proportions of chloride of barium to precipitate the 

 sulphuric acid (No. 4, of course, excepted), and of carbonate of soda to throw down 

 the earths. 



To try the action of these different waters, five copper slips of the dimensions above 

 (4 X 0-5 inch), cut from the same sheet, were suspended in a pint each of the fol- 

 lowing samples of water:— 1. Heart of the Gulf-stream. 2. The same, with the 

 weed. 3. Caribbean Sea. 4. Falmouth harbour. 5. Plymouth harbour. After 

 thirteen days they were taken out and reweighed, having been put in all bright, 

 but cleaned, on taking out, only with a brush in soft water, as in the other experi- 

 ments ;— 1. 2. 3. 4. 5. 

 Loss in thirteen days 181 0'26 0-4 0-46 0-31 



Nos. 1. 3. 4 and 5. were placed in a hot-house window, to assimilate to a hot 

 climate. No. 2. being too offensive for this place, was put just beneath an unceiled 

 southern roof, where the heat and light were inferior to the others. But the Very 

 small comparative waste of metal in this instance seems to be due to a pellicle on 

 the liquid, constantly renewing after being stirred down. It seems to indicate more 

 destructive action from the air and salt water than from sulphuretted hydrogen. No. 

 1. came out clean and bright; the others with tarnished surfaces, except No. 2, 

 which was blotchy and speckled. 



These experiments require to be repeated. The Falmouth water presented no in- 

 dications of being more corrosive than that of Plymouth ; and the great difference of 

 waste in these two cases may be due to some unobsei-ved difference of conditions. 

 The excessive action of the Gulf-stream water can hardly thus be explained ; not only 

 the quantity wasted, but the metaUic cleanness of the surface, show a manifest dis- 

 tinction. 



But to whatever extent the recently increased waste of sheathing may be charged 

 upon the greater velocity, more constant employment, and greater consequent liabi- 

 lities of weather and climate of our shipping, particularly of the commercial class, as 

 well as to difference in the nails, there is reason to fear the fault is still to be sought, 

 too often, in the copper itself. The Quarantine Cutter, generally at anchor in Cat- 

 water, was coppered in October 1832, and her copper is now in a very good state. 

 Her last sheathing held good fourteen years. The Eddystone tender, which also 

 moors in Catwater, was coppered in July 1838, and is now in much worse condition 

 than the Quarantine, which has been on service six years longer. That the waste on 

 the Eddystone tender is not owing to her work, appears from the fact that her water- 

 hne, which suffers the wash and friction, continues sound (from a cause to be pre- 

 sently explained); the damage going oa below, where the copper peels off in blue 

 flakes. That .this is attributable, in great degree, to her occasionally grounding upon 

 the black mud, which generates sulphuretted hydrogen and other corrosive matters, 

 is very probable ; the other never grounds, and does less work. Yet the difference 

 is ^ery great to be thus accounted for ; the one being in good condition after nine 

 years' wear, the other coming to patch at the end of three. On neither was there 

 any mark of electro-chemical action by the nails. The Tartar frigate, again, had her 

 copper almost destroyed in four years, though never out of Sheerness harbour ; and 



