1 7ft Tinned Iron. [Book VI. 



the ruft, which would prevent the adhefion of the tin 

 to their furface ; thty are then wetted with a folution 

 of fal ammoniac, and plunged into a vefTel con- 

 taining melted tin, the furface of which is kept co- 

 vered with pitch or tallow to prevent its calcination. 

 The tin adheres to each fide of the plate, and in- 

 timately combines with the iron to a certain depth, 

 which renders the tinned plates lefs difpofed to har- 

 den by being hammered, and forms an excellent 

 defence for the iron againft the action of air and 

 moifture. 



Bifhop Watfon propofes it as a queftion of fomc 

 importance, whether iron of a greater thicknefs 

 might not be advantageoufly tinned ? He defired a 

 workman to break off the end of a large pair of 

 pincers, which had been long ufed in taking the 

 plates out of the melted tin ; the iron of the pincers 

 teemed to have been penetrated through its whole 

 fubflance by the tin j it was of a white colour, and 

 had preferved its malleability. It is ufual to cover 

 iron ftirrups, buckles, and bridle bits, with a coat 

 of tin, by dipping them, after they are made, into 

 melted tin ; and pins, which are made of copper- 

 wire, are whitened, by being boiled for a long time 

 with granulated tin in a ley made with alum and tar- 

 tar. On thefe circumftances he founds two queries; 

 i. Whether the iron bolts, ufed in fhip building, 

 would be preferved from rufting by being long boiled 

 in melting tin? 2. Whether it would be_poffible ta 

 filver iron-plates, by fubftituting melted filver for 

 melted tin? 



It is cuftomary, in fome places, to alloy the tin 

 ufed for tinning iron plates with ^boitt one-fevemieth 

 part of its weight of copper. Too much copper ren- 

 ders the plates of a blackifh hue, but when added to 



tin 



