372 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Dec. 



A similar experiment in brine, or the saturated solu- 

 tion of common salt tested as above for dissolved 

 air . . . . . . „ 1-4 



Wrought iron wire : — 



Twenty pieces of iron, weiijhing 374 grains, im- 

 mersed for HO days in fresh water . . lost I 9 grains. 



A similar experiment in sea water . . „ 20 



A similar experiment in brine • . . „ 0"1 



Cast iron ; — 



Three rods of cast iron, weighini; 787 grains, im- 

 mersed for C2 da>s in fresh water . . lost I'G grains. 



A similar experiment in sea water . . „ 20 



A similar experiment in brine , . „ 0'4 



On comparing logellier the loss of weight of metal in the fresh water, 

 sea water, and brine, it will be observed, that in sea water the corrosion is 

 about one third more than in fresh water ; while in brine, the loss of weii,'lit 

 is about one-fourth part of the loss in fresh water, and one-lifth part of that 

 experienced in sea water; showing that brine possesses corisidfrable 

 power for preserving metals from corrosion. The carbonates of potash and 

 soda are still more efl'ectual in arresting oxidation ; for in saturated solu- 

 tions of these salts, iron wire remained immersed for sixty days without 

 any amount of corrosion being detected. The surface of the plate of zinc, 

 when taken from the brine, was the same as at the commencement of the 

 experiment, excepting in three spots, where there was deep corrosion. The 

 principal of these being around the point, where the copper wire connected 

 the plate with the negative element. The dilference shown between fresh 

 water and sea water, in their power of oxidizing metals, is in the reverse 

 order of the quantities of oxygen dissolved by them, as given in the pre- 

 ceding experiments ; where the sea water is to the fresh as 78 to 85. The 

 principle on which the preserving power of alcohol is attempted to be ex- 

 plained may, in like manner, be here applied to pure water. Although the 

 experiments on the corrosion of iron were continued for eighty days, the 

 dillV-rence between the action of common water and brine may be made 

 apparent in one day. In the fresh water, the hydrated peroxide of iron is 

 Seen forming; while in the brine, only a slight tinge of a greenish infusion 

 can be detected, a sure indication of the scarcity of oxygen. 



The experiments given to determine the respective rates of corrosion in 

 fresh and sea water, are only correct for pieces of metal wholly immersed 

 in them. Where the surfaces are subject to be wet and dry, the corrosive 

 effect of sea water will greatly increase ; on the same principle that iron 

 once coated with rust, decays much faster after the rust has provided a 

 oJgmeut for moisture. Take for example a bar of iron in a field, and a 

 similar piece on the deck of a ship. On the first, the dew of night deposits 

 water, which corrodes until the return of the sun dries it all olf. On the 

 second, on the deck, it deposits spray, which acts like the dew, until the 

 sun dries it oft'; but when dried, there is left a thin deposit of salt, with 

 a powerful uOioity for moisture, which ou the return of evening will attract 

 moisture from the atmosphere, long before the dew wets the metal in the 

 field. Thus it is that a coating of salt or rust, keeps metals much longer 

 in a wet state, than if their surfaces were clean. 



RinKtrbs. — The experiments which showed that brine (by which term, 

 be supposed, a saturated solution of common salt in waur was meant) 

 should be found to be less corrosive of iron than sea water, was consistent 

 with the circumstance, that less air was contained in v\'ater which was 

 saturated with any solid substance, than was contained iu water only 

 slightly impregnated with such substance, and there was no doubt, but 

 that the atmospheric air performed a principal part in the oxydation of 

 iron, which v\as exposed to the weather. Air containing water in solution, 

 corroded iron rapidly ; aud water containing air in solution did the same; 

 and alternate exposure of iron to water aud to air, corroded it still more 

 rapidly ; particularly when by the warmth of the sun, and the blowing of 

 the wind, the film of water which was left on the surface of the netted iron 

 was evaporated, or dried away from that surface, before a fresh wetting 

 occurred. Perfectly dry air was very slightly, if at all, corrosive of iron, 

 aud water completely freed from air by boiling, was not actively corrosive, 

 in the manner that air and water were. Kespecting salt, there was nothing 

 corrosive of iron in its own nature; it cimtained no oxygen, but althoug'i 

 it was a great cause of corrosion of iron, the corrode<l iron was found to be 

 an oxide, not a muriate of iron. The salt when dissolved in water, greatly 

 increased the corroding ell'ect upon iron which was immersed in the salt 

 water, aud still more if the iruu was frequently wetted, or washed with 

 salt waier and dried by the sun and tlie wiud, lu the intervals between suc- 

 cessive wettings. The concurreut tifect of air, water and salt, was ex- 

 tremely corrosive of iron. It was well known, that dry salt was not at all 

 corrosive of iron, for in stoveo fur drying salt, the iiues were frequently 

 made of iron plates, aud the salt iu lumps being laid directly upon the irou, 

 did not corrode it at all, the iron being always kept hot and dry ; in the 

 same stoves, if they were not used, and allowed to cool, the salt absorbed 

 liumidity from the air, and became very corrosive of the iron work. Iron 

 salt-pans, for boiling brine, did not become oxydated as rapidly as might 

 be expected ; indeed, they were scarcely afl'ected at the parts of the up- 

 right sides of the interior surface of the pans, which were always beneath 

 th:^ surface of the hot brine aud were not exposed to the action of tire. The 

 manner in which salt operated, to increase the oxydation of irou, w as pro- 

 bably by an electro-chemical action, the chief part of the oxygen which the 

 iron absorbed, being derived from the atmospheric air, the other part from 

 the water, and uone from the salt. In heaps of old iron exposed to water, 

 it might be observed to lodge lu the hollows, and to occasion rapid rusting 



of the iron, attended by a smell of hydrogen, and a thin pellicle floatingon 

 the surface of the water, showing dingy prismatic colours. The paper 

 which had been read, mentioned absorption of oxjgen from the air by 

 wat-^r; it was generally understood, that when water absorbed air from 

 the atmosphere, the nitrogen of the air, as well as the oxygen, were both 

 absorbed together by ihe water, in their accustomed proportions, as they 

 existed in the atmosphere, so as to be an absorption of atmospheric air by 

 the water. 



Mr. Low E said the paper led to the consideration of the change which was 

 induced iu cast iron, by continued immersion in various fluids. This bad 

 been frequently discussed at the Institution, and it would be desirable if 

 Mr. A<lie would continue his experiments, with a view to elucidating that 

 question, as the cuuversion of cast-iron into carburet of irou, or graphite, 

 appeared, under certain circumstances, lo be so rapid, as to have rendered 

 necessary the substitution of other aud more expensive inelals. In brewe- 

 ries, for instance, the change had been produced so very speedily, where- 

 ever the acid wash came into contact with metal, that copper gratings had 

 been of necessity substiluied for cast iron. 



Sir JoH.N IfLNNiii, President, stated, that the earliest example in his re- 

 collecliun of the change produced by sea water in cast iron, was in some 

 iron guns which were fished up in 1822 oft Holyhead. 'I'hey were sup- 

 posed to have belonged to a pirate vessel which was destroyed there about 

 100 years previously. M'hen found they were quite soft, but after exposure 

 to the air fur a time, they became so hard, that they were used to fire 

 salutes, when George the IVth passed through Ho!}head, on his way lo 

 Dublin, and it was remarked that the report from them was louder lliaa 

 from any other irou guns of a similar size. 



REVIE^VS. 



Turning and Manipulation. By Charles Holtzapffel, Vol. II. Illus- 

 trated by upwards of 700 woodcuts. Hultzapftel. Loudon : I846. 8vo. 



This large octavo volume of upwards of 500 closely printed pages, is 

 only one of a series of six. in which the subject of Mechanical Manipula- 

 tion is intended to be comprised. The first volume (reviewed, u«(e, vol. 

 VI, p. 1843), treated of the properties of various materials used in the arts, 

 and their preparation, &c. The present volume describes the various 

 kinds of cutting tools used by the hand, such as boring tools, saws, and 

 planes, and their modification when worked by steam-engine power. The 

 third volume will refer to abrasive processes, such as grinding and polish- 

 ing ; Ihe fourth to simple hand turning ; the fifth to complex turning; the 

 sixth to amateur mechanical engineering. It is intended that the first three 

 volumes should form a general preliminary work with an index in com- 

 mon. 



The volume before us is of so thoroughly technical a nature, and afl^brds 

 the most minute and practical information on the subjects of which it treats ; 

 at the same time, it is written aud arranged iu a very perspicuous mauuei , 

 and abounds with interesting accounts of successive improvements of dif- 

 ferent machines, the extraordinary perseverance aud skill of the mechani- 

 cians to whom these improvements are due, aud the beautiful accuracy of 

 their final results. While therefore the chief value of this work will be the 

 practical guidance which it affords respecting peculiar classes of industrial 

 art, it has also an interest for the general reader, and especially lo the en- 

 gineer pursuing some branch of his profession collateral to that here con- 

 sidered, because it exhibits to him the important mutual dependence of the 

 arts to each other. The introductory chapter (the 22nd of the work) gives 

 general remarks ou cutting tools, the variations of the cutting angle of the 

 tool, (that is the inclination of the surfaces meeliug at its edge) and the 

 variations of the angle of inclination to tlie material to be cut, which of 

 course depend on the hardness of the material. 



In the next chapter the plane aud planing machine and their modifica- 

 tions are described, together with a great deal of minute information about 

 joiuers' benches, bench stops, adjustment of bench planes, aud other 105 steries 

 of the workshop. The subsequent chapter treats of turning tools for hard 

 aud soft woods, ivory, brass, iron, and steel, aud the nianipulatiou of these 

 instruments. Next conies a chapter on drills of all kinds, watch drills, 

 press drills, ratchet and lever drills, corner drills, dift'ereutial screw drills, 

 &c. The following chapter is a most interesting one upon cutting ma- 

 chines, and traces ihe consiruction of the screw from the simple method 

 invented by Pappus to the most refined processes of modern art. The four 

 following chapters are devoted to saws, tiles, shears, and punches, respect- 

 ively, and the application of tliose instruments ou a large scale by steam 

 or other engine power. 



We offer the following extract from the chapter on screws, of an account, 

 which we have ourselves read with great iuterest, of the successive iiu- 



