24: 



NA TURE 



[April 29, 1909 



pages; it would have been advisable to split up the 

 subfamilies into sections, and so to subdivide the kevs 

 into more handy form. A word of special praise must 

 be accorded to the general editing and indexing of 

 these two volumes, a task that has been most efficiently 

 and conscientiously carried out. R. S. 



COAL MINING. 

 Practical Coal Mining. By Leading Experts in Mining 



and Engineering-, under the Editorship of Prof. W. S. 



Boulton. Divisional Vol. VI. Pp. viii+ 177-449. 



(London : The Gresham Publishing Company, n.d.) 

 ' I "HIS volume forms the final instalment of the 

 -1- above-named book, and brings to a conclusion 

 this somewhat heterogeneous collection of articles re- 

 lating to coal mining. The fifth volume was noticed 

 in Nature of October i, 1908, and it concluded in the 

 midst of an article by Mr. A. H. Cooke on mine 

 surveying, the entire article consisting of five chapters ; 

 for reasons best known to themselves the pub- 

 lishers have here again given an example of their 

 irritating practice of concluding a volume in the midst 

 of a paragraph. 



Mr. Cooke's contribution maintains throughout a 

 high standard, and in the absence of any modern 

 British text-book on the subject is more especially 

 welcome. He quite rightly lays stress upon the 

 importance of triangulation for the purpose of survey- 

 ing the surface of mining royalties, and his description 

 of the field work of triangulation is very good and 

 complete ; the only omissions that we have noted, and 

 these are not very important, are those of the use of 

 such modern alloys as " invar " for bands for base- 

 line measurements, and some reference to the employ- 

 ment of satellite stations, when trigonometrical 

 stations, otherwise highly suitable, are not ac- 

 cessible for setting up the theodolite. It would 

 have been well to have devoted some space to 

 the office work and calculations required, especially to 

 the methods for calculating the coordinates of the 

 triangulated points direct by the use of traverse tables 

 alone. 



It might also be pointed out that whereas a chapter 

 has been devoted to the correlation of underground and 

 surface surveys, there is no mention made of the impor- 

 tant portion of the mine surveyor's duties that is com- 

 prised under the general head of "setting out," e.g. 

 the laying out of surface and underground roadways, 

 curves, &c. ; yet the latter is almost a daily part 'of 

 the surveyor's routine work, whilst the former, im- 

 portant though it certainly is, constitutes an e.xcep- 

 tional operation that has only to be performed at long 

 intervals. "^ 



The second article, by Mr. S. W. Price, deals with 

 the preparation of coal for the market. It is a great 

 pity that more space was not devoted to this subject, in 

 view of its great and daily increasing importance, and 

 of the fact that the literature on the subject is so 

 scanty. This latter reflection justifies the expression of 

 some surprise that the author has not made use of 

 the best— almost the only— contribution to his subject 

 in modern British literature, namely, the report of the 

 committee of the Mining Institute of Scotland on coal 

 KO. 2061, VOL. 80] 



cleaning, which he might have consulted with much 

 advantage. The present article contains three chapters, 

 the first on the handling and tipping of coal-tubs, the 

 second on screening and picking coal, and the third 

 on washing coal. The first two are entirely satis- 

 factory, but the third is too short and sketchy, and is 

 decidedly weak, especially in the theoretical portion. 

 Thus the author seems to rely almost wholly on the 

 principle of equal falling in order to explain the action 

 of the jig or bash, without making it at all clear that 

 in these appliances the regime of equal falling (when 

 the particles are falling with practically uniform velo- 

 city) is never really reached ; it is, moreover, not quite 

 correct to say with Pernolet that a particle reaches 

 this ultimate velocity in the first second of its fall, 

 because the time required to reach this condition 

 depends upon the size and density of the particle, and 

 may be much more than a second or only a fraction of 

 that time. The author quotes Maurice and Bring with 

 equal approval, or, if anything, lays more stress on the 

 conclusions of the former, although Bring reaches his 

 as the result of a vast amount of experimental work, 

 whilst those of Maurice are mainly deduced from 

 mathematical reasoning, which is, moreover, vitiated 

 by the fact that it is all based on the assumption that 

 the resistance offered by the water (or viscosity, as 

 Maurice wrongly calls it) varies always as the square 

 of the velocity of motion of the particle, whereas this 

 relation is only approximately correct when a certain 

 velocity has been attained, and is therefore not true in 

 the initial stages of falling. 



Prof. VV. Gallowav contributes an excellent article 

 on coke ovens, dealing exclusively, however, with 

 retort and by-product ovens. He has gone almost 

 exclusively to Germany for his data, and has succeeded 

 in condensing a large amount of very valuable and 

 not generally accessible information into his article. 



The last article is on the economics of coal, by 

 Messrs. H. S. Jevons and David Evans. This difficult 

 subject is dealt with here far too briefly, and the 

 writers do not seem to have the intimate technical 

 knowledge that is required to discuss this subject 

 thoroughly, though it is only right to say that in deal- 

 ing with a subject like this, on which every writer has 

 views of his own, wide differences of opinion 

 are naturally to be expected. Thus to many it 

 would seem that the authors' classification of 

 the demand for coal is not satisfactory, and 

 that a sharp line should be drawn between the 

 demand for furnaces, factories, and the like, and 

 the demand for transport purposes, by railways, and, 

 above all, by steamships, the economic effects of these 

 two requirements being quite different. The authors 

 have included the requirements for manufacturing and 

 for transport under one head, and thus obscure the 

 results of certain conditions that are economically of 

 distinct importance, as, for example, the effect that the 

 annual closing of the Baltic Sea to navigation in 

 winter has upon the price of coal. Further, it might 

 be objected that the question of the life of a colliery 

 and the necessity of the corresponding amortisation of 

 the capital invested in the shafts and other permanent 

 works has not received the consideration which this 

 very important subject deserves. Henry Louis. 



