524 



NA TURE 



[August i, 1901 



mind has an independent existence from eternity, mono- 

 theism seems to disappear. On the other hand, if mono- 

 theism is insisted on, what becomes of the free-willing, 

 independent minds, the citizens of the republic of minds ? 

 We are expected somehow to accept what look like con- 

 tradictory propositions simultaneously. Again, all minds 

 are different from one another and yet all are straining 

 towards the same ideal. Here is a sentence that aims 

 at explaining this : — • 



" In fine, its self-definition {i.e. the self-definition of 

 each spirit) is at the same stroke in terms of its own 

 peculiarity, its own inerasable and unrepeatable piirticu- 

 /(jr//)', and of the supplemental individualities of a whole 

 world of others — like it in this possession of indestruct- 

 ible difference, but also like it in self-supplementation 

 by all the rest : and thus it intrinsically has wiiversality " 

 (P- 353)- 



We have left little space for the discussion of the essays 

 that deal less directly with the main argument. One of 

 them gives an interesting account of later German philo- 

 sophy, another deals with, the "art-principle in poetry." 

 The essay on the " Right relation of reason to religion " 

 is certainly the best. Everywhere in the book, but most 

 of all in the last-mentioned essay, we feel that the author 

 is a man who hates any notion that is in itself or in its 

 implications degrading to human nature. In religion he 

 boldly rejects authority and bases it on reason, defined as 

 the mind's own insight, as its true source. 



There is much in the book that it is good to read. The 

 author hates pessimism ; most of all he hates determinism 

 as a belief that unnerves the character and robs human 

 life of what is best in it. But he has found no philosophic 

 basis for his views. In fact, we have in this book an in- 

 stance of what is not uncommon : a man's opinion is 

 often of far greater value than all the reasons he is able 

 to give for it. 



COAL MINING. 

 A Text-Book of Coal-Mining. By Herbert W. Hughes- 

 4th edition. Pp. 513: 670 figures. ''London: Griffin 

 and Co., Ltd., 1901.) Price 26,s. net. 



MR. HUGHES and his publishers may fairly be con- 

 gratulated on the success of a text-book which 

 requires a new edition about once in every three years, 

 and this, too, in spite of its high price, which is beyond 

 the means of the average student. The new edition 

 contains ninety more pages and 1S4 more illustrations 

 than the first. 



It can hardly be expected that a large treatise of this 

 description should be free from some minor errors ; but 

 when these are decidedly numerous, one cannot help 

 feeling that there is want of care on the part of the 

 author. Mr. Hughes seems to think (p. 3) that reversed 

 faults are rare ; surely he can never have carefully 

 looked at the sections of some of the Continental coal- 

 fields. On p. 4, while speaking of the Carboniferous 

 system in Scotland, he appears to be ignorant of the coal 

 in the Calciferous Sandstone below the Carboniferous 

 Limestone. 



The chapter on boring is weak ; it may be said with 

 a good show of truth that the colliery engineer nowadays 

 frequently entrusts the work of boring to a contractor ; 

 NO. 1657, VOL. 64] 



but this is an argument for omitting the chapter alto- 

 gether, rather than for treating the subject in a slovenly 

 fashion. There is no figure of a derrick of any kind. On 

 p. 22 it is stated that the American boring tool is rotated 

 by hand ; this was done formerly, nowadays turning by 

 hand has been given up. The rotatory and percussive 

 systems of boring are mixed up in a manner puzzling 

 to the student, for the description of the diamond drill 

 says: "This method differs from the others in the fact 

 that the tool receives a rotary instead of a percussive 

 motion"; and yet just above, on the very same page, 

 Mr. Hughes has been describing Davis's calyx drill, 

 which works by rotation. 



Timbering is not treated so fully as one v;ould 

 like, and we scarcely think that Haselmann would be 

 content to hear his process of preserving timber spoken 

 of as similar to the Aitken process. 



An author should be consistent. In speaking of the' 

 transmission of power (p. 46), it is said that the choice is 

 limited to compressed air and electricity, and yet a little 

 further on we have a description of Brandt's drill, which 

 is driven by water. 



Mr. Hughes is wrong in supposing that the "straw" 

 cannot be employed for igniting charges of explosives 

 other than gunpowder. He is a little behind the times 

 with regard to water injection while boring, as he makes 

 no mention of Bornet's system, which is an unquestion- 

 able improvement upon the method tried at Blanzy in 

 1889, and not 1899. 



Granted that some knowledge of electricity on the part 

 of the mining engineer is nowadays desirable, if not im- 

 perative, is it not better that he should obtain the rudi- 

 ments of that knowledge first-hand from an electrician 

 rather than second-hand from a miner ? Why should 

 the writer of a mining text-book think it his business to 

 explain the electrical units? Mr. Hughes evidently ex- 

 pects the student to learn elsewhere what is meant by 

 such terms as "limestone,'' "sandstone," "horse-power," 

 "symbol," "molecular weight"; why then does he go out 

 of his way in the case of electricity, upon which subject 

 there is ample published information ? As a consequence, 

 we find the mistake of defining the ampere as " the 

 quantity per minute." 



In the same way, it would be better to leave the ques- 

 tion of generation of power to an expert. Steam-boilers 

 are mentioned in a somewhat cursory fashion, and all 

 other modes of generating power ignored. One of the 

 statutory fittings to the boiler, viz. the safety valve, is 

 described, but the other two, the water gauge and the 

 steam pressure gauge, are not noticed. 



On page 432, Mr. Hughes revives the old question 

 whether the introduction of safety lamps will not produce 

 an increase in the number of deaths from falls of roof and 

 side. Statistics have shown that this fear is ungrounded, 

 and it is a pity to throw doubts upon the subject. 



While calling attention to the existence of very numer- 

 ous minor defects, one cannot be blind to the useful 

 w^ork which Mr. Hughes has done in compiling what is 

 unquestionably the best text-book on coal-mining in the 

 English language, and for keeping it up to date. For 

 this he well deserves the thanks of students and mining 

 engineers. Plate II., reproduced from Mr. Hughes' own 

 photographs, is excellent. 



