Faraday to John Barrow   1 January 1838

Royal Institution | 1 January 1837 [sic]

Sir

I beg leave to acquaint you for the information of My Lord Commissioners of the Admiralty that I have seen Mr. Wall1. Mr. Wall objects to let me know what his preparation is or to leave with me a sample of prepared copper for trial experiments2[.] I can therefore observe upon what he states to me[.]

Mr Wall professes to have covered copper with a substance which at the same time that it will protect the copper from the contact & therefore from the action of sea water will adhere to it in a manner far surpassing that of varnish paint or any other known substance used for such or similar purposes. Now water frequently exerts an extraordinary power of making such coatings strip off from metals as in the air would adhere perfectly and before our opinion could be formed on this point the copper prepared in the way proposed ought to be exposed to sea water both below the surface & at the water line both light and air having free access at the same time[.] Such trial made against a piece of lacquered copper & a piece of painted copper & perhaps also a piece of tarred copper placed in exactly similar circumstances would illustrate the adhesive power well[.]

Next as to the resistance of the chemical action of sea water the same kind of trial would illustrate that point and would be required before a useful opinion of the proposed method of preparation could be given[.]

But when a ship is passing through the waves her bottom is subject to mechanical action as well as chemical action and plates of the prepared copper ought to be exposed to a strong run or stream of sea water for the purpose of ascertaining what alteration will occur. It is an opinion of some that even copper itself is abraded & in part carried away by the wash of sea water against it. But whether that be so or no any coating used to cover it ought to have its powers of resisting the mechanical action of water put to the test[.]

Finally if the coating to the copper were found to be so effective as to protect entirely according to Mr Walls expectation I should expect as almost a necessary consequence that plants & barnacles &c would adhere to a ship coated with such copper just as they do to a copper bottomed vessel over protected upon the principle of Sir Humphry Davy3[.]

I have the honor to be | Sir | Your Very Obedient Servant | M. Faraday

Sir John Barrow | &c &c &c &c


Endorsement: 3 Jany Ack Rect and express their Lordships thanks on the occasion.

Surveyor for information to be released.

Unidentified.
Faraday had been asked by the Admiralty, on 26 December 1837, to examine Wall's copper sheets. Admiralty Digest PRO ADM12 / 334, 59.9.
See James (1992).

Please cite as “Faraday1056,” in Ɛpsilon: The Michael Faraday Collection accessed on 29 March 2024, https://epsilon.ac.uk/view/faraday/letters/Faraday1056