1840.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



415 



sandstone, yielding 44 per cent., and at Brisham, yielding G2 per cent. 

 The Devon and Cornwall ores are used extensively in South Wales, 

 as also a rich heematite from the neighbourhood of Bristol, containing 

 from 45 to liO per cent. The iron of ores of the Forest of Dean are 

 found like those of Cumberland in the carboniferous limestone ; brush 

 ore is one of the principal varieties, a hydrate, with protoxyde of iron, 

 containing frequently from tiO to 65 per cent, of iron, the leaner ores 

 containing a great deal of calcareous matter in the shape of spar, and 

 so yielding only about 15 or "25 per cent. The Forest of Dean ores 

 are the only ores worked alone, and instead of being treated with lime- 

 stone, require a mixture of burnt argillaceous schist, as on account of 

 their containing liu^estone, they are refractory and infusible. 



We now come to the iron stones — these are commonly found in 

 horizontal strata, subject to the same acclivity and declivity as the 

 other stratified substances under the surface; their inclination varying 

 according to the nature of the ground, and the disposition of the in- 

 cumbent "strata. They are supposed to be of aqueous origin, and are 

 generally found imbedded in scliistous clay more or less compact, 

 which moulders away on being exposed to the atmosphere, and fre- 

 quently accompany coal and limestone, in immediate contact with the 

 coal. The ores are of two principal forms, in strata from half an inch 

 to twelve inches thick; regularly connected strata called bands, and 

 strata of detached stone found in distinct masses, from the size of a 

 small shot up to a weight of several hundred pounds. The smaller 

 masses being called in Scotland ball stones, and the larger lunkers (qy. 

 lumpers). Band ironstone accompanying limestone is most commonly 

 of inferior quality, its component parts being chiefly calcareous, and 

 the quantity of iron contained being small, while ball iron stones ac- 

 companying lime are of much superior quality. The iron stones are 

 divided by Mr. Mushet into four classes. 1. Argillaceous ironstone, 

 which has clay for its chief component earth, and this clay compara- 

 tively pure and free from sand. 2. Calcareous ironstone, possessing 

 lime for its chief mixture, and this lime also comparatively destitute 

 of sand. 3. Siliceous ironstones, uniting clay and lime, and containing 

 large proportions of silex. 4. Mixed ironstone, containing nearly an 

 equalized mixture of clay, lime and sand. Each of these classes re- 

 quires a different treatment dependent on its constituent parts, which 

 with the quality of the fuel are the causes of the great diversity of 

 processes which prevail in the manufacture of iron. Besides these 

 four classes must be mentioned the Muslietstone or Blackband, a car- 

 boniferous ironstone, partaking much of the nature of coal as generally 

 it contains carbonaceous matter enough to terrify the stone and make 

 it (it for the furnace. Its exact geological position has not yet beer, 

 determined, but is supposed by its discoverer to be in the lower part 

 of the coal field near the millstone grit. The usual criterions by which 

 ironstone is judged are — 1, the degree of tenacity with which it ad- 

 heres to the tongue after torrefaction ; 2, its colour ; 3, the obedience 

 to the magnet when pulverized; 4, by depriving of its iron a given 

 weight of the ore in the assay furnace. The first and third of these 

 methods are peculiarly liable to error, as the degree of adhesion to the 

 tongue will be more in proportion to the quantity and kind of clay 

 contained in the stone, than to its real contents of iron, and the in- 

 fluence of the magnet as before remarked, is equally deceptive. The 

 test by colour, although an empirical method, is one far more to be 

 depended upon. A correct chemical analysis, however, although the 

 surest test, is scarcely ever used, from the ignorance of the manufac- 

 turers. Mr. Mushet complains loudly and truly of the deplorable state 

 of scientific knowledge of this class, which is as slow in acquiring in- 

 structions as in adopting improvements. He asserts that to his own 

 knowledge the grossest mistakes have been made, and cites one case 

 of iron ores of 30 per cent, having been sold for and smelted as ores 

 containing GO per cent. Detection it appears in such cases is difficult, 

 as the charge of the furnace often consists of an association of iron 

 ores, iron stones, and scoria from the forge and mill. Nor does the 

 case appear to be much better among those professing some know- 

 ledge, as from want of proper instruction they are also open to gross 

 errors. Instruction of this kind therefore seems to be a legitimate 

 object in schools of mining and engineering, the inculcatiob of which 

 would be of more good than all the attempts at teaching practice by 

 theory. 



A Practical 

 Pambour. 



By the Comte de 



Treatise on Locomotive Engines. 



London : J. Weale, 1840. 

 We feel much gratification in being enabled to recommend to the 

 notice of those of our readers who are interested in the theory or 

 practice of locomotive endgines, a second edition of this excellent and 

 truly valuable work. The former edition, although conveying, in the 

 form of experiments, more practical information relative to locomotives 

 than any other work which has appeared on the subject, and embody- 



ing the results of those experiments in a theory, which, though no 

 perfect, was nevertheless calculated by the soundness of the reasoning 

 in general, to throw much light on the true theory, was still defective 

 in several points. The resistance of the air to the motion of the 

 trains, and that of the extra pressure of the waste steam on the back 

 of the pistons, caused by the blast-pipe, did not enter into the evalu- 

 tion of the work done by the engines. To supply these deficiencies, 

 the author undertook, in the month of August, 1S36, some experiments 

 on the Liverpool and Manchester Railway, from the results of which 

 he has deduced formultB for determining those quantities which had 

 previously been neglected in the calculation of the resistance over- 

 come. 



These experiments comprise also several other researches, such as 

 the vaporization of boilers in different circumstances of rest and 

 motion, the effects of different proportions between the fire-box and 

 the tubes on the total vaporization of the engine, and on its consump- 

 tion of fuel, &c. 



In the first edition the loss of steam by the safety valves had been 

 very incorrectly measured ; this has suffered a material alteration in 

 the edition now before us, but how far the new determinations are to 

 be depended on, remains yet to be proved. It is an investigation 

 which demands that the experiments should be conducted witli the 

 utmost nicetv, and in the greatest possible variety of circumstances. 



The table'of experiments on the quantity of water carried over with 

 the steam in the liquid state, differs in some respects from that which 

 was published in our Journal for December, 1S30, and to which we 

 appended a note explaining our reasons for not putting implicit confi.- 

 dence in the results obtained. Two different experiments with the 

 Star engine have been substituted in the work under consideration, 

 for those contained in the table which was published in the Journal, 

 and in all the other experiments which are the same as in that table, 

 w-e observe that a different deduction has been made for the loss by 

 blowing through the safety-valves during the asceut of the plane. 

 The first of our objections is removed by the indirect statement that 

 there was no loss by leakage during the experiments given in the 

 table, the second in some measure by the corrections in the determi- 

 nation of the loss through the valves, and the last by the declaration, 

 that the mean is only intended to be adopted approximatively for 

 engines that have not been directly submittea to experiment in this 

 respect. This mean has been corrected from 0-GS to U-70. 



The second chapter, which treats of the laws which reg\ilate the 

 mechanical action of the steam, is the same as the corresponding 

 chapter of the " r/ieon/ of the Steam Engine,'" by the same author, 

 which vpas published last year. It has been introduced here in order 

 to save the reader the trouble of recurring to another work, besides 

 which, it has the advantage of rendering unnecessary the purchase of 

 that work to those who are only interested in steam engines in as 

 much as they are applied to the purpose of locomotion on railways, 

 and whose means may be too limited to justify such an addition to 

 their libraries. 



We are compelled, for want of time, to postpone a more particular 

 examination of this very interesting w^ork until next month, in the 

 mean time assuring those of our readers who are desirous of making 

 themselves more thoroughly acquainted with the ettects of locomotive 

 engines, that they cannot do better than possess themselves of this 

 second edition of Comte de Pamboiir's Treatise ; for those who were 

 unable to obtain the first edition, will be amply recompensed for their 

 disappointment, by the superiority of the new one, and those who 

 possess the former, will find it almost equally necessary to purchase 

 the latter, since it can scarcely be considered as a reproduction of the 

 same work, but almost rather as a continuation of it, so many and 

 important are the corrections and additions which have been intro- 

 duced. 



REPORT ON THE REMOVAL OF THE WEIR AT THE BROOMIELAW 



BRIDGE, GLASGOW. 



By William Bald, F.R.S.E.. M.R.I.A.. &e.. Engineer of the Clyde. 



To the Trustees/or Improviitg the River Clyde and the Harbour of the City 



of Glasgow. 

 My Lord, and Gentlemen, 



In conformity with the remit transmitted to me, dated the 6th instaut, I 

 have read over the Report of Captain Jolmstone and Mr. Russell, Harbour 

 Masters. It has been drawn up with great care ; and from the facts therein 

 stated, is of great value, and merits deep attention. I have no hesitation in 

 signing their report, so far as it treats of the many advantages which would 

 arise from the opening up the spaces between the bridges for the accommo- 

 dation of the small steamers, sailing craft, &c. But there are other points, 

 in my opinion, of vital importance, connected with this subject, which have 

 not been mentioned in their report ; and which I beg lea^ e to lay before 

 your lordship and the trustees. 



