220 



NA TURE 



[July 8, 1897 



Add to this the fact that the fair sex have not the strength 

 or any of that recuperative power necessary in case of 

 emergency that man possesses, and that they suffer many 

 fold from the ever-disturbing wind resistance in conse- 

 quence of the garments which fashion imposes upon 

 them, and that because of these same garments they are 

 in sorry plight in case of a moderate accident ; with all 

 this in the mind of a mere reasoning person, there is no 

 wonder that he thinks of something else, the degree 

 question at Cambridge for instance. Had the suburban 

 ladies been given another year or so before the desire 

 to ride a bicycle extended so far in the direction which 

 is known from a mere social point of view as upward, 

 it is possible that the change of attire would have 

 spread gradually, and that now, or perhaps in a year 

 or two, suitable costume would have been adopted as 

 readily as the cycle jargon and slang so often met with. 

 Ladies start with every natural disadvantage, and then 

 they proceed to magnify them in a more effective way 

 than their conscious ingenuity could devise. 



The chapter on wheels is one which will be read with 

 interest by riders especially. Here will be found a de- 

 scription of the author's tangent wheel, in which the 

 spokes are not fastened to the hub at all ! It is almost 

 impossible to believe at first that spokes held in pairs 

 to the hub by merely having their common centre portion 

 wound a fraction of a turn round the hub will hold 

 sufficiently tight to withstand all the twist that a strong 

 rider can exert upon them. But the theory is convincing, 

 and especially when steep-angled grooves are employed 

 in which to lay the wire, no doubt can remain that this 

 is the case. 



Ball-bearings form the next subject, and these are 

 treated far more thoroughly and scientifically than is 

 usual. The actual want of absolute perfection in the 

 ordinary bearing is pointed out, and a number of sug- 

 gestions made for bearings in which the balls approach 

 as near as possible to the state of pure rolling. The 

 ordinary ball-bearing answers so well, in spite of the 

 spinning and rubbing friction which accompanies the 

 rolling, that it is hardly likely that the more elaborate 

 bearings, in which these defects are reduced or abolished, 

 will take their place. At the same time, a discussion of 

 them is of educational value to designers. 



Chains and chain-gearing are dealt with very 

 thoroughly and completely. There is one omission, 

 however, which must be noticed, and that is all reference 

 to the results of Hans Renold, of Manchester, who found 

 that a small difference of pitch is desirable in the driving 

 and driven wheel. The writer of this notice picked up 

 one of Renold's pamphlets at a cycle show some years 

 ago, and was much struck with the arguments there used. 

 It may be that this is all common knowledge, or that it 

 is mistaken ; but either way, one would like to have had 

 Mr. Sharp's views upon the subject. 



Mr. Sharp explains the correct method to setting out 

 chain wheels for Jong-link and for block chains ; he is 

 not afraid of criticising one of the chief companies. 



" In Humber pattern chain-wheels the teeth are often 

 quite straight (Fig. 451). This tooth form is radically 

 wrong." 



On page 417, Mr. Sharp points out a defect in a 

 usual pattern of chain which the practical man would 

 NO. 1445. VOL. 56] 



hardly expect. Here the plates of the chain are cut away 

 on the side next the chain-wheel, so that the line joining 

 the rivets is not in the middle of the portion that is left. 

 If the plates were cut away on the other side as well, so 

 as to leave less metal, they would be stronger still. In 

 the next page there is a suggestion which seems valuable, 

 namely, to make the side plates of metal which has been 

 stretched beyond its elastic limit, and which therefore 

 has an increased rigidity. As these links can never be 

 subjected to compression, the objection to this procedure, 

 which is met with in other cases — as, for instance, in 

 Southard's twisted cranks— does not apply. 



The bicycle chain is a more marvellous piece of 

 mechanism than is generally supposed. The pins have to 

 bear a force which is far greater than is prudent in 

 ordinary structures, while the bearing surface of the 

 blocks on the rivets have in use occasionally to bear more 

 than twice the amount given by Prof. Unwin as the 

 maximum value for bearings on which the load is inter- 

 mittent and the speed slow. 



The discussion on the variation of relative speed in the 

 driving and driven wheel is curious rather than important. 

 One result of the rules given by Mr. Sharp for shaping 

 the teeth of sprocket wheels is that even in elliptical 

 wheels the teeth will have the same form as in circular 

 wheels of any size, so that the same cutters can be 

 employed for all wheels if adapted to the tooth face, and 

 not made simply to plough out the space between two 

 teeth at one cut. 



The practical reader would like to know whether the 

 tooth forms recommended work well in practice, for there 

 is undoubtedly much prejudice in favour of the patterns 

 of our standard makers, whether condemned by Mr. 

 Sharp or not. 



Toothed-gear wheels are treated at length. The theory 

 is, of course, common knowledge, but it is very well put, 

 and the results of a paper on circular-wheel teeth, pub- 

 lished by the author in the Proceedings of the Institution 

 of Civil Engineers, are given also. Toothed-wheel gears 

 follow. The mechanical reader who is not already ac- 

 quainted with these, will be surprised at the ingenuity and 

 perfection which are embodied m this class of work. 



There is much remaining unnoticed, but the length to 

 which this review has reached is such that many interest- 

 ing points cannot be even mentioned. 



" Bicycles and Tricycles," by Sharp, has taken its place 

 as the one standard book which ought to be found where- 

 ever cyclists do congregate, and which no one designing 

 or inventing any detail connected with a bicycle should 

 fail to possess. C. \. Bovs. 



THE GEOLOGY OF THE BRITISH ISLES. 



Geological Map of the British Isles. Originally com- 

 piled by Sir Archibald Geikie, LL.U. Revised and 

 extended by Alexander Johnstone, F.G.S. (Edinburgh 

 and London : W. and A. K. Johnston, 1896.) 



Mineralogical Geology : a Synopsis for the Use of 

 Students. To accompany W. and A. K. Johnston's 

 Geological Map of the IBritish Isles. By Alexander 

 Johnstone, F.G.S. (Same publishers as above, 1897.) 



THE first of these works is by a long way the best and 

 most convenient geological map of the British Isles, 

 both for lecturers and students ; and this new and greatly 



