Royal Society. 59 



The principle of varying or modifying chemical energies 

 by those of electricity has been applied by the invention, in a 

 manner the most philosophical, and on a scale the most ex- 

 tensive. 



The copper sheathing of ships and vessels had been found 

 to corrode in the short period of a single voyage, being con- 

 verted into an oxide through the medium of some acid, or at 

 least of a decompounded substance, occupying the negative 

 extremity of the electric scale. The copper must therefore be 

 positive in respect to tbe body decomposed or attracted. A 

 reference was made by the Government to the Royal Society, 

 with the hope of discovering some remedy for this most serious 

 evil. Grounded on a perfect knowledge of chemical and of 

 electric powers, it immediately occurred to the illustrious dis- 

 coverer of their relations one to the other, that if a substance 

 more positive than copper, and in contact with it, could be 

 exposed to the corroding action, that the copper would, by 

 induction, be rendered less positive, and therefore indisposed 

 to combine with any other negative body. 



Experiments the most satisfactory were then made on a 

 small scale ; and in consequence of their success, plates of 

 zinc, and afterwards of iron, were applied to ships' bows ; and 

 the copper has been fully and completely protected. The 

 theory and the experiments have been confirmed in the most 

 ample manner. A defect has indeed occurred in practice, from 

 the over success of protection. The induction of negative 

 powers to the copper has gone too far ; they have caused it to 

 act on the compounds in an opposite direction, by attracting 

 to itself the earths and alkalies, thus affording attachments to 

 the marine vegetables which the copper was intended to pre- 

 vent. This appears to me, however, susceptible of a cure. 

 I am sufficiently advanced in years to remember the American- 

 revolution war. Ships were then first sheathed with copper : 

 they were preserved clean from weeds, nor was the copper 

 corroded : but the ships were fastened together by iron bolts, 

 and these, to the utter astonishment of every one, decayed; and 

 the ships became unable to sustain the ordinary straining in 

 gales of wind. For some time the effect could not be traced 

 to its cause, for galvanism was then unknown; but at last 

 bolts made of bronze were substituted for those of iron, and 

 immediately the copper failed. When the theory has therefore 

 been modified by experience on the principle of these empiric 

 trials during the American war, I cannot hesitate in predicting 

 complete practical success ; with full glory to the illustrious in- 

 dividual who deduced the practice from theory, and with ample 



I 2 advantage 



