04 ANNUAL OF SCIENTIFIC DISCOVERY. 



1. A spike, taken without selection from a lot of several thousand 

 pounds, was driven its length into sound white oak timber. A block, in- 

 cluding the spike, was exposed alternately to diluted muriatic acid, and 

 air, several days. Every minute opening in the copper was thus found, 

 the iron reached, and a portion dissolved. The resulting salt of iron, and 

 the tarmic acid of the wood, gave a bluish black discoloration to the wood. 

 Exposure to the air caused the formation of hydrate of peroxide of iron, 

 which, filling the minute openings, prevented further action. Oa splitting 

 the block, it was found that the general surface of the spike was unaltered ; 

 the iron having been dissolved from those points only where pores or 

 openings had existed, remained as a salt adhering to the spike. - 



The destruction of iron in sea- water takes place through the absorption 

 of oxygen ; the exfoliation of the oxide permits the action to continue, 

 until the strength and size of a bolt become reduced. In the case of these 

 spikes, as the copper remains firm, only minute surfaces of the iron are 

 reached, and where oxide forms, these little orifices which are first made, 

 become closed, and no further action occurs. 



In this experiment the acid was a thousand times more powerful than 

 sea- water is, and the effect, in point of time, was greatly increased. 



2. Into vessels adapted for the collection of hydrogen, iron bars and 

 copper coated spikes were separately placed. A mixture of muriatic acid 

 and water was added in like quantity to each. The hydrogen which would 

 in this case be evolved, being measured for a given time, denoted the com- 

 parative rapidity of solution, for equal surfaces. It was soon found that 

 the iron, of nearly equal surface, evolved so much greater volume of hy- 

 drogen, that the quantity of surface could be much reduced ; and Avhen it 

 equalled only one -fourth the surface of one spike, and four such spikes 

 were used, the spikes gave one volume, while the iron afforded nineteen. 

 This experiment was varied, and continued six days, and a mean result 

 for rapidity of solution, where the iron was one-sixteenth the volume of 

 the spikes, was as one to nineteen and five-tenths. If the iron surface of 

 the copper- covered spikes at the pores in the copper dissolved with the same 

 rapidity as nail-rod does, the exposed surface of spikes would there- 

 fore require 304 times as many days for destruction in this way, as iron 

 ones would. 



Under any conditions to which these spikes can be exposed to corrosion, 

 they will have at least the comparative duration of nineteen times that of 

 iron pikes not coated, in sea-water ; and as they retain their size unaltered, 

 they will remain firm in their places. 



TIN FOILS CROOKE'S PATENT. 



My invention consists in such improvement in the manufacture of tin 

 foils and sheets, that by it I accomplish the reduction of the cost, though 

 retaining those qualities which are essential to the purposes for which such 

 foil or metal is required This I effect by combining the baser and cheaper 



