Changes of Curvature by Means of a Flexible Lath. 465 



I scarcely think that Prof. Pucker is justified in stating 

 that I have pat forward anything which can legitimately be 

 termed a " new solution " of these results — a one-break 

 representation instead of a four-break one — or that " in the 

 heat of argument " I have abandoned discontinuities on 

 which I previously insisted. The simple fact is that I now 

 find that a more complicated bent-lath curve or parabola will 

 fit over the one particular break as to the existence of which 

 I, from the first, expressed my doubts, but that even now I 

 consider that there are objections against the use of such a 

 curve, and, I may mention, I have found more objections 

 since I stated this in my previous paper. It is true that, for 

 the sake of comparison with Prof. Pucker's results, I extended 

 the curves a short way beyond the two other breaks at the 

 two ends, but this was effected, as I pointed out in the foot- 

 note on p. 141, only at the cost of increasing the apparent 

 error to the extent of about one quarter as much again as that 

 of my original drawing, and also of that of the experimental 

 error. 



The present state of the case may, I believe, be summarized 

 as follows : — The chief argument in favour of the interpre- 

 tation which I gave of my experiments was the concordance 

 of the results 'obtained from various sources. Prof. Riicker's 

 criticism starts by ignoring this argument, or, at any rate, 

 does not attempt to explain how such a concordance was 

 obtained, and deals only with a portion of one set of results. 

 Prof. Pucker admits that these results show in places, either 

 breaks, or something very like breaks, and he therefore con- 

 fines his attention to a portion where all the changes are 

 " minor " ones. He admits that the bridging over of these 

 supposed breaks by a single equation does not necessarily 

 disprove that they really are breaks, and all that he does is to 

 construct such an equation, but an equation in favour of 

 which as an expression of physical facts nothing can be 

 urged. If the terms in this equation have no physical 

 meaning then, I venture to think, it cannot be accepted as 

 an expression of physical facts ; whereas, if they have a 

 physical meaning, then it is legitimate to analyze the 

 equation, and by so doing we obtain, as I showed, additional 

 proof, instead of disproof, of the very changes which I con- 

 sidered existed. 



I quite agree with Prof. Pucker that further discussion, at 

 any rate on these restricted lines, is useless. A mathematical 

 investigation must be obviously confined to some special 

 instances, and these instances must be worked up to a higher 

 pitch of perfection than was possible in a work of which the 



