MODERN INVENTIONS. 549 



ture, as it has to be suspended from the mast-head, and dragged through 

 the water, and is always liable to entanglement upon the lowering of 

 the upper masts. But it will be apparent, that in whatever position we 

 suppose the sliding masts to be placed, whether in a state of elongation 

 or of contraction, still the line of conduction, by Mr. Harris's arrange- 

 ment, will remain perfect ; for that part of the conductor which neces- 

 sarily remains below the cap and top, when the sliding masts are struck, 

 is no longer in the line of action, and consequently its influence need 

 not be considered. 



In describing the lightning conductors, we have mentioned copper 

 sheathing, which has been hitherto held to be the best protecting medium 

 for ships' bottoms ; but as the vessel in which we are embarked is sup- 

 posed to be constructed of iron, and is only intended to navigate " the 

 sunny seas of fancy," she needs no such covering : were it otherwise, we 

 should have adopted 



WETTERSDETT'S PATENT METALLIC SHEATHING, which is an alloy 

 of lead, antimony, and quicksilver^ the combination of which is such 

 as not only to preserve them from oxidating, but also imparts to the 

 composition peculiar qualities of cohesion, tenacity, and elasticity, 

 qualities which are not possessed by copper or its alloys generally, and 

 which render the patent material highly eligible for the purpose to 

 which it is applied. The cohesion of the particles is not destroyed by 

 a violent strain or blow, as copper is affected, but being exceedingly 

 elastic and tenacious the metal adapts itself to the force of the percus- 

 sion. Its tenacity also gives it a ready adaptation to surface, which is 

 of considerable importance, not only in facilitating the perfect covering 

 of the vessel, at first, but subsequently in obviating the effects of any 

 accidental strain the vessel may receive during her passage, and which, 

 under ordinary circumstances, might occasion the loss of the ship, cargo, 

 and crew ; and it will be found equally useful in the event of a vessel 

 -being driven on shore. After use, the outward surface of this marine 

 sheathing remains perfectly clean and bright, like silver, without any 

 adhesion of barnacles, or other marine productions, such as were found 

 to be so great a means of obstruction in the experimental trials of Sir 

 Humphry Davy's Protector, notwithstanding the philosopher's conclu- 

 sions, a priori, that a negative state of electricity would be unfavourable 

 to vegetable production or existence. The chief points of superiority 

 possessed by Mr. Wettersdett's sheathing over that of copper, are, that 

 it is not subject, like the latter, to oxidation, and consequent destruc- 

 tion, or to the accumulation of sea-weed, barnacles, or other material, 

 which retard the speed of the vessel ; to which may be added, that this 

 combination of metals acquires additional hardness by being kept in 

 contact with the sea ; that it is of considerably less price than copper ; 

 and that it is far more durable than sheathing made of the last-named 

 metal. 



Let us return upon deck, and complete our survey. Here we have 



WATSON'S LIFE PRESERVER, and is at once light, elegant, and yet 

 perfectly serviceable. It is formed of two hollow spheres of copper, 

 hermetically sealed, each being about twelve inches in diameter. These 

 spheres are united by a cord, of sufficient length to permit a man to 

 place himself between the spheres, and obtain support in the water by 

 hanging over the cord, or getting it under his arms ; the atmospheric 

 fluid contained in the spheres being enough to afford sufficient buoyancy 



