Miscellanies. 205 



was corroded, and this preserved the copper; most effectually in the 

 vessel where both metals were in contact, and the copper was corro- 

 ded, more and more, as it receded from that point. Sir H. Davy's gal- 

 vanic protection of the copper sheathing on ships, is well known, and 

 its failure arose, from a very unusual cause, namely, its perfection : 

 the marine shell fish, being no longer, as before, poisoned by the solu- 

 tion of the corroded copper, collected in enormous quantities, during 

 long voyages, and thus retarded the sailing of the ship. Perhaps the 

 experiment has been too hastily abandoned, and had its illustrious au- 

 thor lived, in his accustomed vigor and zeal, he might, not improbably, 

 have modified his protection by zinc or iron, to that degree which 

 might have afforded both a poison for the sea insects, and adequate 

 protection for the copper. The public are acquainted also with the 

 ingenious experiments of Dr. John Revere, on the same subject ; 

 they appeared very nigh to entire success, but we are not aware that 

 any trials of the kind are now making on a large scale. Capt. Scott's 

 suggestion as to the cause of the protection afforded by the iron pins 

 to the copper sheathing is undoubtedly correct, and although it might 

 not be expedient to resume the iron pins, it might be entirely judi- 

 cious to attach a very small portion of iron or zinc to every sheet of 

 sheathing on a ship's bottom. 



Capt. Scott, being about to sail again for Holland, kindly proffered 

 his services, which were gratefully accepted, for the purpose of bring- 

 ing home any interesting notices that might fall in his way respecting 

 foreign science and arts. 



After remarking, that " a high scholar once told him that if shipmas- 

 ters would sometimes make use of their eyes and ears, abroad, they 

 might add much to the stock of science at home," he adds, that he saw 

 at Rotterdam a galvanic magnet, of six or seven pounds power. This 

 was doubtless of the same general construction as that of Professor 

 Joseph Henry, described two years ago in this Journal. It will be 

 remembered that the latter lifted more than two thousand pounds and 

 with some additions that have since been made, it would now lift 

 probably several hundred pounds more. 



20. Prize offered by the Imperial Academy of Sciences, of St. Pe- 

 tersburg, at its public sitting December 22d, 1832, and January lOtky 

 1833. — Communicated by John Vaughan, Esqr. of Philadelphia. 



The experiments of Gay-Lussac and Thenard upon the manner 

 in which potassium acts in amraoniacal gas, have brought to light a 



