The results he produced are equally interesting and important, whether we contemplate them biographically, as indicative of the peculiar genius by which they were obtained; or, scientifically, in their connexion with the electro-chemical theory, to the farther developement and illustration of which they have so powerfully contributed; or, economically, as the probable means by which the hand of Time may be averted, an increased durability imparted to rapidly perishable works of art, and monuments of human genius transmitted to posterity, in all their freshness, through a long succession of ages. It is probable that, in the earliest period of naval architecture, some expedient[85] was practised, in order to protect ships' bottoms from the ravages of marine worms.[86] The use of metallic sheathing, however, is of ancient date. The galley supposed to have belonged to the Emperor Trajan was sheathed with sheets of lead, which were fastened with copper nails.[87] The same metal was also used in the earlier periods of our naval history;[88] and it is worthy of remark, that the circumstances which led to its disuse, were the rapid corrosion of the _rother irons_, (from the formation of a Voltaic circle,) and the accumulation of sea-weed. [85] Mr. Knowles, in his "Inquiry into the Means which have been taken to preserve the British Navy," observes, that the first sheathing was probably the hides of animals covered with pitch, or with asphaltum, which led to the use of thin boards, having, in some cases, lime, and in others lime and hair, between them and the bottom of the ships. [86] The worms infesting the timber of ships are--the _Teredo_, the _Lepisma_, and the _Pholas_. The first of these, however, which was imported from India, is by far the most destructive; and I am informed by Mr. Knowles, that it is more abundant at Plymouth than on any other part of the coast where there is a dock-yard; and although on the shores of England it is not of a very large size, yet it is a formidable enemy to the safety of those ships which have not a metallic sheathing to cover their bottoms. In the East Indies, and off the coast of Africa, the _Teredo_ is of very large size; and holes have been bored by them in the timber of at least seven-eighths of an inch in diameter. [87] Alberti Archeti. [88] In the year 1670, an Act of Parliament was passed, granting unto Sir Philip Howard and Francis Watson, Esq. the sole use of the manufacture of milled lead for sheathing ships; and, in the year 1691, twenty ships had been sheathed with lead, manufactured by them, and which was fastened with copper nails.--See _Knowles's Inquiry_.