342 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[November, 



stone contain only minute quantities of carbonate of magnesia. 

 An I'Xiimiiiation or those in Weyer's cave in Virginia liad proved 

 tliat wliile the niilivy white opaque stalactites contain a small hut 

 measurable amount, the sparry and more transparent kinds are 

 almost destitute of a trace of this ingredient. It is evident that 

 in such cases the carbonate of magnesia is carried oif by the liquid 

 below, and that such is the case seems to be confirmed by the fact 

 of the large amount of carbonate of magnesia found in the springs 

 in tlie immediate neighbourhood of the cave just named. 



5. A fact of much interest noticed in these experiments, is the 

 comparative readiness with which the magnesian and calcareo- 

 magnesian silicates yield to the decomposing and dissolving action 

 of carbonated water and even simple water. This explains the 

 rapid decomposition of most rocks composed of hornblende, 

 epidote, ike, without calling in the agency of an alkali; and it 

 enaldes us to trace the simple process by which plants are fur- 

 nished with the lime and magnesia they require from soils contain- 

 ing these silicates without our having recourse to any mysterious 

 decomposing power of the roots of the growing vegetable. 



6. In their tache experiments, the Profs. Rogers ascertained that 

 the powder of anthracite, bituminous coal, and lignite, all yielded 

 a discernable amount of alkali to the cai'bonated water, while the 

 ashes of these materials similarly treated gave no alkaline trace 

 on the test paper. This, they think, is at once explained by the 

 high temperature at which tiie ash is formed, which by experi- 

 ments already noticed is quite sufficient to dissipate any portion of 

 alkali or carbonate originally present in the material. 



Remarks. — Mr. Pattinson stated that he had patented a process for 

 separating magnesia from the magnesian limestone. Tlie process consists in 

 forcing carbonic acid to dissolve the magnesia, whereas it will not dissolve 

 the lime. 



2. Report on the Oxidation of Rails in and out of use, determining 

 the Loss by Abrasion. By Mr. R. Mallet. 



The top surface of a railway-bar in use is constantly preserved 

 in a state of perfect cleanliness, freedom from oxidation, and polish; 

 while the remainder of the bar is rough-coated originally with 

 black oxide, and soon after with red rust (peroxide and basic 

 salts). Not only is every metal electro-positive to its onn oxides, 

 but, as established in the second Report on the Action of Air and 

 AVater on Iron, the polished portion of a mass of metal partially 

 polished and partially rough is primarily corroded on the rough 

 portion. Hence a railway-bar while in use is constantly preserved 

 from rusting by the presence of its polished top surface. Such 

 polished surface has no existence on the rail out of use. The 

 upper surface of the rail in use is rapidly condensed and hardened 

 by the rolling of the traffic over it; and it is also shown in the 

 above Report that, all other circumstances being the same, the 

 rate of corrosion of any iron depends upon its density, and is less 

 in proportion as this is rendered greater by mechanical means. As 

 every metal is positive to its own oxides, the adherent coat of rust 

 upon iron, while it remains, powerfully promotes the corrosion of 

 the metal beneath, and this in a greater degree in proportion as 

 the rust adherent is of greater antiquity. It has been shown that 

 the rust produced by air and water, which at first contains but 

 little per-oxide, continues to change slowly, and becoming more 

 and more per-oxidised, becomes more and electro-negative to its 

 own base. Now, the rust upon a railway-bar out of use continues 

 always to adhere to it, and thus to promote and accelerate its cor- 

 rosion; while the rust formed upon a railway-bar in use is per- 

 petually shaken off by vibration, and thus this source of increased 

 chemical action removed. 



To recapitulate, railway-bars forming part of a long line, whe- 

 ther in or out of use, corrode less for equal surfaces than a short 

 piece of the same iron similarly exposed. Rails in use corrode 

 less than those out of use. This difference is constantly decreas- 

 ing with the lapse of time. The absolute amount of corrosion is 

 a source of destruction of the rail greatly inferior to that due to 

 traffic. It is highly probable that the electrical and magnetic 

 forces developed in the rails by terrestrial magnetism and by 

 rolling traiHc re-act in some way upon the chemical forces con- 

 cerned in their corrosion; aiul that, therefore, the direction of 

 lines of railway in azimuth is not wholly indifferent as respects 

 the question of the durability of rails. 



The author concludes with two practical suggestions, deducible 

 from the information obtained: — 1st. Of whatever quality iron 

 rails are rolled, that they should be subjected prior to use to an 

 uniform course of hammer-hardening all over the top surface and 

 sides of the rails; and, 2ndly, that all railway-bars before being 

 laid down should, after having been gauged and straightened, be 

 heated to about 400° Fahrenheit, and then coated with boiled coal- 

 tar. This has been proved to last more than four years, as a 



coating perfectly impervious to corrosive action, while constantly 

 exposed to traffic. 



.3. Anah/tical Investigations of Cast-iron. By Mr. AVniGnTSON-. 



The analyses showed the influence of the hot blast in producing 

 the so-called "Cold Short Iron," by occasioning an increased 

 reduction of phosphoric acid, and the consequent increase of 

 phosphorus in the "hot-blast" iron. The respective per centages 

 were — 



1 I 2 I 3 I 4 ] .1 I fi I 7 

 Cold Blast .. 47 U-11 0-31 (fin 21 0-OM 0:tS 

 Hot Blast .. 0-51 I 5.^ j 0-60 1 071 ] 0-^4 | 0*ur [ 0-4D 



The irons differed also considerably as to the state in which the 

 carbon was contained in the hard white iron, resembling impure 

 steel, containing nearly all its carbon in a state of chemical com- 

 bination, whilst the carbon contained in the grey and mottled 

 varieties of iron was principally contained only as a mechanical 

 mixture. The presence of sodium and potassium in all the speci- 

 mens examined was also noticed for the first time, and it was 

 thought probable that these might materially affect the qualities 

 of the metal. 



liemar/is. — Mr. Phillips pointed out the loss of carbon, which, in the 

 method described, would arise from the use of hydrochloric acid, giving rise 

 to an oily product; to which Mr. Wrightso.v replied tliat he had determined 

 the carbon by an independent method. — The President inquired if Mr. 

 Wrightson had sought arsenic in all liis analyses ? — Mr. Wrightson replied 

 that be had not found it in some, and did not, in consequence, look for it in 

 the others. — The President objected that it was as important to determine 

 the absence as the presence of so important an element as arsenic. In reply 

 to an inquiry, be said that in examining the slags of furnaces in many coun- 

 tries, he had only discovered phosphoric acid in one from Belgium. 



4. On Copper containing Phosphorus, with details of Experiments 

 on the Corrosive Action of Sea-Water on some varieties of Copper. 

 By Dr. Percy. 



Upon analysing a specimen of copper, to which when in a state 

 of fusion some phosphorus had been added, it was found that it 

 contained a considerable quantity of phosphorus, and also a large 

 portion of iron derived from an iron rod employed in stirring the 

 mixture at each addition of the phosphorus. The copper employed 

 was of the "best selected" — it appeared to be harder than copper 

 treated with arsenic. The details of the analysis of 116'76 grains 

 were given, the result of which was — 



Phosphorus 0*93 



Irou l-y9 



A second analysis gave — 



Copper 9.572 



Iron 2-41 



Phosphorus 2'41 



100-.54 



It has long been stated that a very small quantity of phosphorus 

 renders copper extremely hard, and adapts it for cutting-instru- 

 ments — but such an alloy as that formed by Dr. Percy has not 

 previously been formed. It is a remarkable fact that the presence 

 of so large a quantity of phosphorus and iron should so little 

 affect the tenacity and malleability of the copper. The effect also 

 of phosphorus in causing soundness in the casting of copper is 

 interesting, and may be of practical importance. 



Remarks. — Captain James, superintending engineer at the Woolwich 

 dockyard, said that the rapidity with which copper sheathing sometimes de- 

 cays was surprising; in five months it sometimes decays completely. Some 

 of the old copper had lasted forty years ; and for the purpose of determining 

 the cause of this difference, he made a series of experiments on all the 

 copper which had been used in her Majesty's dockyard. By steeping these 

 different coppers in salt water for nine months, a series of actions set in, 

 which, by subsequent weighing, were accurately determined. The following 

 table exhibits the results of these experiments : — 



Grains. 



Klectrotype copper, loss per square inch 1'4 



Selected copper 1 • 1 



Copper containing phosphorus ■(.) 



Copper from the " Kloric" VI 2 



dockyard copper. No. 1 l-(i6 



Uitto No. 2 3' 



l>iUo No. 3 2-43 



Ditto No. 4 2'a3 



Rlunts's metal -yj 



Mr. Phillips inquired if the specimens were wholly exposed to the water, 

 or were only partially exposed, so as to allow the action of air ; as in the 

 latter case the chloride of magnesium in sea-water would give rise to the 

 formation of an oxichloride, but which would not be formed if air were 

 absent. — Captain James said they had been wholly immersed. 



5. On the Formatioyi of Dolomite. By Professor Forchhajumeb. 

 The white chalk of Denmark is covered by a bed only a few feet 

 thick, containing corals of the genera Caryophyllia and Oculina, 

 and a number of fossils different from those of the white chalk; 



