THE president's ADDRESS. 337 



and be continued 6 or 7 hours, the surface becomes so hard as to 

 resist a rasp file, and will bear any amount of exposure to weather. 

 This oxidizing process does not affect the surface in any other way 

 than by turning it black, so that even polished surfaces retain 

 their smoothness. But if there should be the slightest flaw in the 

 ■film or coating of oxide, rust will be formed at that spot, but at" 

 that spot only, for the rust does not spread laterally under the 

 black oxide, as it frequently does when the iron surface is covered 

 with paint, or varnish, or cement, nor has the rust the least 

 tendency to detach the magnetic oxide film from its subjacent 

 parts. 



The application of this process for preserving iron will no doubt 

 in time extend to almost everything for which iron is used, and 

 it can be conducted at a venj small cost. The muffle in which 

 Professor Barff has carried on most of his experiments hitherto 

 measures about 4 feet deep, 3 feet wide, and about 3 feet high. 

 This and the adjoining apparatus for the superheated steam, 

 both of which are of simple and inexpensive construction has been 

 worked at a cost of about 3s. for fuel, and you can understand 

 how many dozens of small things may be operated upon at one 

 time, in the chamber I have described, and upon which small 

 articles the extra cost of oxidizing will be quite unappreciable. 



Among the uses to which this process may be applied, I may 

 mention the preservation of mining pumps, water mains, water 

 connecting pipes, the lining of which with the magnetic oxide 

 would resist friction, gas pipes and nipples, and the substitution 

 of oxidized iron pipes for lead pipes. It will be valuable for 

 architectural purposes, both in the construction of buildings, and 

 for decorations ; for railway girders and bridges, railings, lamp 

 posts, iron safes, for this oxide coating if exposed to great heat 

 expands and contracts with the iron without leaving cracks for 

 the rust to enter. Need I mention its value for screws, rivets, 

 and bolts. Experiments are being made for gun barrels, and for 

 the protection of steam boilers, and for the plates of iron ships, 

 both outer plate and inner, for sometimes certain cargoes have 

 been known quickly to corrode ships' plates, and thus have led 

 to the sudden loss of iron trading vessels. The power of this 

 magnetic oxide to resist the effects of salt water may be learnt 

 from specimens of magnetic iron ore from New Zealand and 



