On the Use of Zinc for covering Buildings. 345 

 its previous brittkriess, but may be beut aud applied to 

 many uses for which it has bteu hitherto thought unfit." 

 These observations being now generally circulated, the nia- 

 iiuFacturers have used it ; and with so much success, that 

 what was before almost useless in the mechanical arts, is 

 now wrouglit and sold in plates similar to copper. About 

 two years since, I took an opportunity of trying whether or 

 not it could be adopted for the purpose of covering build- 

 ings; for I conjectured, if it could, that it would be a most 

 valuable acquisition to the public, particularly at the present 

 time, when lead and copper are so exorbitantly dear as in 

 ijome measure to supersede their use. I laid it on a tempo- 

 rary building (for experiment only) in bays, like the mode 

 pursued with lead, and in a situation exposed to the most 

 trying heat and inclemency of this climate, and no change 

 is yet visible, except in colour, which is rather darker; nor 

 does it appear at all oxidated ; nor is there that appearance 

 of unevenness in the suri'ace, as is the case with thin lead 

 and copper covering : its partial brittleness, however, makes 

 it necessary to put it on in a dit^erent manner to what lead 

 is, and in the shape of the roll only, which, mslcad of a 

 plain round, should resemble that of an inverted cinja-recta^ 

 -which, by forming the internal angle into an easy hollow, 

 will obviate the danger of cracking on hammering it down^ 

 which would almost invariably follow by adoptir.g the other 

 niode. I have been thus particular in describing this pre- 

 caution, knowing the consequence of an error arising from 

 the other plan. Zinc will be found extremely useful and 

 (Decononiical for all kinds of pipes, gutters, &c. ; and there 

 can be no doubt of its being well adapted for the sheathing 

 of ships, and, indeed, for almost all the purposes to which 

 lead and copper are applied. Its hardness, according to 

 Thomson, is 6|", when lead is only 5-i-" ; it n.elis at a tem- 

 jjerature of 700" of Fahrenheit, while kad is fluid at 540*. 

 It is well known in the arts, and has been the subject of 

 much curious analysis by the chemists. It was called zinc 

 by I'aracelsus, who, there is reason to believe, was the first 

 who succeeded in obtaining it pure; it has also been called 



spelter ; 



