424 Facts about Iron. 



claimed for many of them. On this subject, however, much 

 information is still wanted, and when fine steel is produced, it 

 by no means follows that it owes its qualities to a minute 

 portion of some other metal, or non-metallic substance con- 

 jectured to have affected it beneficially. It is of course quite 

 possible that minute additions may produce great results ; but 

 if we may judge from Dr. Percy's book, very little has been 

 accurately ascertained. One alloy of 80 parts zinc, 10 copper, 

 and 10 iron, is said to possess very valuable working proper- 

 ties, and not to rust in moist air. 



Dr. Percy also mentions Mr. Eckman's process of case- 

 hardening by arsenic. Rasped leather, or other nitro- 

 genous animal matter, is made into a sort of porridge with 

 hydrochloric acid and arsenious acid. The metal is painted 

 over with this composition about one-sixteenth of an inch 

 thick, and then heated in a muffle to bright redness. A white 

 surface of arsenide of iron is thus obtained, which effectually 

 resists rust. 



The bulky velume from which we have made the preceding 

 extracts forms the second part of Dr. Percy's Metallurgy, and 

 a third part is expected to complete it. The scientific world 

 will unanimously applaud the doctor's labours. He has 

 brought together an amazing mass of facts, which perhaps no 

 one else had accumulated, and a large portion of winch he has 

 for the first time made accessible. He has undoubtedly 

 achieved a great work ; but the second volume, like the first, 

 leaves the regret that his talent for exposition and arrange- 

 ment is not equal to his enormous metallurgical learning. As 

 storehouses of facts, the two volumes are invaluable, but as 

 regards the elucidation of principles, or convenience for refe- 

 rence, they leave much to be desired. 



