290 EIGHTH REPORT 1838. 



The results of these investigations show that zinc is fully ca- 

 pable of protecting cast or wrought iron in sea or fresh water, 

 when applied in a massive form, at least for a time. They also 

 put in a forcible point of view the important part which the 

 contact of air plays in the corrosion of iron. 



86. It would seem, however, to be doubtful how far this pro- 

 tecting power even of zinc is completely permanent, for as a • 

 portion of the oxide of zinc is transferi'ed to the surface of the 

 iron, as Professor Edmund Davy has observed, it would seem 

 that the preserving power of the zinc is diminished. 



A forelock key, now presented, with which I have been fa- 

 voured by Professor Davy, and which has been immersed in sea 

 water for about three years, though protected by zinc in form 

 of a ring loosely connected with it, is yet somewhat acted on, a 

 crust of magnetic oxide being formed all over it, spotted over 

 with the oxide of zinc ; yet the action is incomparably less than 

 it would have been in the same time and circumstances if wholly 

 unprotected. My attention has also been drawn by Professor 

 Miller, of Cambridge, to the curious fact, that the surface of the 

 iron is covered in places with microscopic crystals of calc spar; 

 these he was kind enough to examine for me with the gonio- 

 meter, and although under vex'y disadvantageous circumstances, 

 succeeded in verifying their form as that of the common calc 

 spar rhomb. This fact is interesting, as a new instance of the 

 production of an insoluble crystallized minei'al by galvanic cur- 

 rents of low tension, 



87. Pepys long since proposed to preserve polished instru- 

 ments of iron and steel from rust in air by zinc protectors. This 

 seems to have been unsuccessful, and was found to be so by 

 Professor Edmund Davy. 



88. Very lately a company has arisen in London, under the 

 name of the "British Galvanization of Metals Company," based 

 upon a patent for the protection of iron by coating its surface 

 with fluid zinc, obtained by a French engineer, M. Sorel. I 

 lately wrote to the secretary of this company, and have obtained 

 specimens of the so-called galvanized iron, which are now pre- 

 sented. I also wrote to another company, styled the " Zincked 

 or Galvanized Iron Company" : my letter was returned un- 

 opened by the secretary. Having only received the specimens 

 a very few days before the present meeting, I have been unable 

 as yet to make many experiments upon them ; some, however, are 

 detailed in the prospectus of the company, of Professor Graham, 

 Mr. Children, Mr. Garden, and Mr. Brand, which amount to 

 this, that, as was to be expected, the zinc preserved the iron, in 

 dilute acids, vintil the whole of it was dissolved. In the speci- 



