TINNING, PLATING, &C. 



Thirty hundred weight of cast iron is reduced to twenty, when it is 

 to be made into wire ; and twenty. six to twenty-two, when it is 

 to be made into bar iron. Steel suffers much less loss of weight in 

 being hammered, (han iron does. Cast steel does not lose above 

 two parts, and bar steel not above four, in one hundred, when 

 drawn into the shape of rasors, files, &c. The iron plates in England 

 are not hammered, but rolled to proper dimensions by being put 

 between two cylinders of cast iron, cased with steel. This me- 

 thod of rolling iron is practised in Norway, when they form the 

 plates with which they cover their houses j but whether it was in- 

 vented by the English, or borrowed from some other country (as 

 many of our inventions in metallurgy have been, especially from 

 Germany), I have not been able to learn. In the first account 

 which I have seen of its being practised in England, it is said to 

 have been an invention of Major Hanbury at Pontypool ; the ac. 

 count was writen in 1697, an d many plates had then been rolled*. 

 The milling of lead, however, which is an operation of the same 

 kind, had been practised in the year 1670 ; for an act of parlia. 

 ment was passed in that year, granting unto Sir Philip Howard 

 and Francis Watson, Esq. the sole use of the manufacture of 

 milled lead for the sheathing of ships. A book was published in 

 1691, intitled, The New Invention of Milled Lead for sheathing 

 of Ships, &c. It appears from this book, that about twenty ships, 

 belonging to the navy, had been sheathed with lead ; but the prac. 

 tice was discontinued, on account of complaints of the officers of 

 the navy, that the rudder irons and bolts under water had been 

 wasted to such a degree, that in so short a space of time, as had 

 never been observed upon any unsheathed and wood, sheathed ships. 

 The persons then interested in sheathing with lead, published a sen. 

 sible defence ; and among other things they remarked, that both 

 the Dutch and the English had ever been in the habit of sheathing 

 the stern-posts and the beards of the rudders with lead or copper ; 

 and that the Portuguese and Spaniards did then sheath the whole 

 bodies of their ships, even of their gallions, with lead, and had 

 done it for many years. Copper sheathing has since taken place 

 in the navy ; but it is said to be liable to the same objections which 

 were, above a century ago, made to lead sheathing. It is prefer, 

 able, however, to lead, on account of its lightness. If the fact 



Phil. Trans. Abr, Vol. V, 



