329 



second time, and for ever. The timely subscription was im- 

 mediately successful. The torques had been secured for the 

 Academy ; they were to be presented in the course of the 

 same evening; and, along with the cross of Cong, they would 

 help to form the nucleus of the future National Museum. 

 With such a beginning, it was not too much to expect a 

 rapid progress ; since matters so attractive and important in 

 themselves would naturally tend to draw others around them. 

 The special thanks of the Academy were voted to Pro- 

 fessor Mac Cullagh for his present of the Cross, 



Mr. Mallet gave a notice of the present state of the 

 investigation, entrusted by the British Association to Pro- 

 fessor Davy and himself, upon the action of air and water, 

 whether fresh or salt, and under various modifications, upon 

 cast and wrought iron. From the press of other papers, 

 Mr. Mallet was obliged to confine himself to a very brief 

 notice respecting a new mode of protection which he pro- 

 posed for iron, when exposed to air and water. 



This method is of the electro-chemical class, and is 

 founded on the fact, that the softer and more carbonaceous 

 cast irons, such as the Scotch and Irish, are in a positive 

 condition with respect to the less carbonaceous irons, such 

 as the Welch, &;c., in common use for engineering purposes. 



This difference of electrical condition he has found 

 experimentally to be sufficient to enable protectors of the 

 former sort of iron to be applied to the surface of the latter, 

 with the result of largely preventing the corrosion of the 

 electro-negative metal. This was shown by the exhibition 

 of the results of experiments which had been several 

 months in progress. 



It was also stated, that while tin increases the corro- 

 sion of iron, contrary to the opinion of Sir Humphry Davy, 

 zinc does not seem to possess a protective power wholly 

 permanent, at least in salt water, from the formation on its 



