296 EIGHTH REPORT— 1838. 



water by brass was not only spoken of as a discovery, but also 

 acted upon as such in some of the great public \vorks in Liver- 

 pool," Professor Davy (who was not present when Mr. Hart- 

 ley's paper was read and discussed) lost no time in making Mr. 

 Hartley acquainted with Iiis experiments and views on the sub- 

 ject, which he did in a letter inserted iu " Saunders' News-letter, 

 24th October, 1837." In this communication Professor Davy 

 stated, as the result of his experience, " that brass will not pro- 

 tect cast or wrought iron either in salt or fresh water, 1)ut that, 

 on the contrary, these metals will protect brass from corrosion 

 imder such circumstances at least for a limited time. 



" Professor Davy refers the preservation of the iron under the 

 circumstances enumerated to the mere condition in which it was 

 placed, being such as almost entirely precluded the access of air, 

 on which its corrosion, both in salt and fresh water, depends. 



" Professor Davy was at first led to suppose that Mr. Hart- 

 ley's brass, which was spoken of without any qualification, was 

 the common brass of commerce ; but on learning that its com- 

 position was different, he instituted experiments with Mr. Hart- 

 ley's brass, for specimens of which he was indebted to Mr. 

 Robert Mallet. On trying the eff"ects of this brass on iron in 

 salt water, it had no more ])rotecti)ig power than the glass ves- 

 sel in which the experiments were made. When the two metals 

 were in close contact, the iron presei'ved its original brightness, 

 as was also the case where the iron was in contact with the 

 bottom of the glass vessel ; but all the other exposed surfaces 

 of the iron were cori-oded just as readily as if common brass 

 were used Avith the iron." 



102. In April last I wrote to Mr. Hartley requesting speci- 

 mens of his brass, and of the iron preserved by it. I received a 

 very minute portion of brass, and a piece of iron stated to have 

 been in contact with it, together with a piece of plumbaginated 

 iron, part of a sluice or paddle, through Mr. Gilbert Cummins, 

 with the following letter : — 



"Dock Yard, Liverpool, 23rd April, 1838. 



" Sir, — In Mr. J. B. Hartley's absence from England (he 

 being at present on the continent, and not expected back for 

 some lime) I have to acknowledge the receipt of your letter of 

 the 21st instant, and in accordance A^ith your request have for- 

 warded to your address, by the City of Dublin Company's packet, 

 a small parcel, containing a specimen of the brass composition 

 referred to, and also of the cast iron preserved by it ; the latter 

 is part of the hinge of a large cylinder used as a valve to admit 

 the ingress of sea water into a mill-dam or reservoir ; the brass 

 is a part of the bu?h with which the interior surface of the hinge 



