50 ANNUAL OF SCIENTIFIC DISCOVERY. 



sium, in a molten state, so that when the iron is withdrawn it may 

 easily part with the surplus of the aforesaid chemicals, which should 

 run off like oil. The iron is then to be dipped into boiling Avater, con- 

 taining a certain proportion of cyanide of potassium ; from thence it is 

 removed to a bath for a final washing, and set up on end to dry. All 

 the processes are to be carried on under cover, and before exposure to 

 the atmosphere the iron is to be coated with an asphaltum paint twice, 

 at given intervals ; and again it is to receive two coats after fixing. 

 Of course all the necess-ary planing, drilling, and fitting is to be done 

 preparatory to the indurating. The time the iron is to remain in the 

 bath will vary from one to five minutes, according to the weight of the 

 metal to be operated upon. The elaborate character of the process 

 to which the contractor is rigidly bound, will account for the large sum 

 to be expended in carrying out this part of the work ; 4 per tun is 

 allowed to the contractor for the induration and painting ; Messrs. 

 Morewood will receive from the contractors 5s. per tun as their royalty, 

 which it is estimated will be 1,000. Thus 16,000 is to be spent in 

 this effort to prevent oxidation, no greater proof of which, in its 

 damaging results, can be offered than the case of the cleaning of the oxide 

 (or rust) from the Menai Bridge, from which has lately been removed 

 above 40 tuns of oxide of iron." London Mechanics 1 Magazine. 



Prevention of Ruxt on Iron. Many a valuable hint is to be ob- 

 tained from an intelligent practical laboring man, which may lead the 

 philosopher into a train of ideas that may, perhaps, result in discov- 

 eries or inventions of groat importance. When bricklayers leave off 

 work for a day or two, as from Saturday to Monday, they push their 

 trowel in and out of the moist mortar, so that thy bright steel may be 

 smeared all over with a film of it, and find this plan an effectual reme- 

 dy against rust. In Wren's Parentalia, there is a passage bearing 

 upon this subject : "In taking out iron cramps and tics from stone- 

 work, at least 400 years old, which were so bedded in mortar that all 

 air was perfectly excluded, the iron appeared as fresh as from the 

 forge." In the victualling department at Plymouth, somo years ago, 

 I observed a man lime-whiting the inside of some iron tanks, previous- 

 ly to their being filled with water for the service of the crew and pas- 

 sengers during a voyage : this was to prevent the iron rust af- 

 fecting the water. In London, I have also recently seen men, with a 

 tub of lime-whiting and a mop, smearing the inside of large water- 

 pipes, as security against rust. Oxygen, which is the main cause of 

 rust, is abundant in the composition of both water and the atmos- 

 phere ; and that quicklime has an astonishing affinity for it is 

 evinced in the homely practice of preserving polished steel or iron 

 goods, such as fire-irons, fenders, and the fronts of "bright stoves," 

 Avhen not in use, a little powdered lime beaten upon them out of a 

 muslin bag being found sufficient to prevent their rusting. Another 

 instance, very different and far more delicate, bearing upon the same 

 principles : the manufacturers of needles, watch-springs, cutlery, &c. 

 generally introduce a small packet of quicklime in the same box or 

 parcel with polished steel goods, as security from rust, before sending 

 it to a distant customer, or stowing it away for future, use. These 

 cases arc extremely curious, because, as a general rule, bright steel 

 or iron has a most powerful affinity for oxygen ; consequently it is 



