142 Reply to an erroneous Assertion. [Aug. 



Magazine, has been put into my hands, which contains an arti- 

 cle, signed Samuel Deacon, and entitled " Sir Humphry Davy's 

 Remedy for the Decay of Copper Bottoms, not original." The 

 assertion is founded on the following advertisement in " The 

 World " newspaper, of April 16, 1791 : — " By the King's patent, 

 tinned copper sheets and pipes, manufactured and sold by 

 Charles Wyatt, Birmingham, and at 19, Abchurch-lane, Lon- 

 don." These sheets, amongst other advantages, " are particu- 

 larly recommended for sheathing of ships, as possessing all the 

 good properties of copper, with others obviously superior, 

 which the following extract from a report founded on actual 

 experiment, by Dr. Higgins, clearly demonstrates, viz. that this 

 coating of tin powerfully resists the action of salt water, and, by 

 preventing the corrosion of the copper, operates as a preservative 

 of the iron placed contiguous to it." 



The best answer to this attack we have given already, by 

 laying Sir Humphry Davy's paper, from the Philosophical 

 Transactions, before our readers, from which it is most obvious, 

 that his views have nothing in common, except their object, 

 with those of the patentee aforesaid. As far as the extract 

 given by his advocate, Mr. Deacon, enables me to judge, it 

 seems that the superiority claimed by Mr. Wyatt consists 

 merely in coating the surface of the copper sheets with some 

 substance less subject to corrosion by sea water than that metal, 

 and his idea was probably borrowed from the common practice 

 of tinning culinary copper vessels, — a practice known to, and 

 adopted by, the Romans.* As Mr. Deacon gives no particulars 

 of the mode of applying or preparing these tinned plates, it is 

 fair to infer that there was nothing peculiar to them in either 

 respect, and all the claim that he can possibly make out to 

 originality is in the application of an old fact to a new purpose. 



But it is not on the substitution of tinned copper for plain 

 copper, that Sir Humphry Davy's pretensions to originality rest: 

 it is in the principle on which that substitution, or rather an 

 equivalent and, as w r e shall presently see, a superior process is 

 recommended, that his claims are founded. For the explana- 

 tion of that principle, I refer the reader to Sir Humphry Davy's 

 paper; but 1 will ask, did Mr. Wyatt know, that even though 

 nine-tenths of the tin be worn away from a copper saucepan, and 

 the copper exposed, the vessel may still be used with safety '. 

 Could he have explained the cause, if he knew the fact ? When 

 he prepared his sheets, did he carefully tin the whole surface, 

 or was he aware that if the preservative metal were applied to a 

 comparative speck of it only, it would be equally effectual ? Or, 

 lastly, had he the remotest idea that, so applied, it would act as 



• Stannum illitum anieis vasis saporem gratiorem facit, et compescit sruginis virus, 

 &c— (Plin. Hist. Nat. lib. 34, c 17.) 



