Biographical Memoir of Sir Humphry Davy. 23 



therefore, that the process would be stopped by rendering the 

 surface of the copper slightly negative, and this his experiments 

 on the voltaic pile rendered a matter of easy attainment. The 

 metal which, alternating with copper in the pile, assumed most 

 powerfully the positive state of .electricity, iron for example, or 

 what was still better, zinc, must necessarily produce the desired 

 eflPect. On the experiment being tried, it was found that a 

 single grain of zinc, a small nail of iron, protected upwards 

 of a square foot of copper ; and vessels whose sheathing had 

 been prepared in this manner, performed a voyage to America 

 and returned, without the copper presenting any appearance of 

 oxidation. It was found, however, that strict attention required 

 to be paid to the proper proportions, too great a quantity of the 

 preserving metal rendering the copper too negative, a state in 

 which there was deposited an earthy crust which attracted shell 

 fish and marine plants ; and it is even asserted, that, notwith- 

 standing the accurate solution of the problem regarded in its 

 purely chemical relations, this unforeseen circumstance occasioned 

 the necessity of abandoning the practice altogether. Perhaps 

 Mr Davy would have discovered a remedy for this inconvenience, 

 had not the party whom jealousy had raised against him, ren- 

 dered him unwilling to institute any further inquiries. 



A similar cause had some years before arrested him in a la- 

 bour from which the most important advantages to literature 

 and history might have been expected to result. 



Every one knows the degree of' interest taken by the Prince 

 Regent, now George IV., in the unrolment of the manuscripts 

 found at Herculaneum. He supported a director and several 

 workmen, who had already succeeded in unrolling more than a 

 thousand ; and as every thing encouraged the hope that chemis- 

 try would afford the means of facilitating the operation, Mr 

 Davy was sent to Naples for the purpose in 1818. A careful 

 examination of these rolls, and a strict inquiry into the causes 

 which had reduced them to their present condition, led him to 

 conclude that it would be impossible to devise a simple method 

 of softening them ; but he suggested numerous improvements 

 on the plan followed, which were received with expressions of 

 gratitude by the conservators of the collection. Another scien- 

 tific Englishman, however, skilled in the study of manuscripts, 

 Mr Elonsby, having attempted to decypher some of those which 



