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 apse 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 10th, 
1833.—Communicated by John Vaughan, Esqr. of Philadelphia. 
The experiments of Gay-Lussac and Thenard upon the manner 
in which potassium acts in ammoniacal gas, have brought to light a 
