SOLID MEASUREMENTS. 227 



standard foot. I agree with my friend Dr. Siemens, that if we could 

 only have one measure it would be a great thing for all countries, and I 

 would go into the matter at once if the standard yard and our standard 

 inch would only divide into the metre, but unfortunately it will not ; 

 and as all our screws and all our machinery are made to the standard 

 inch, of course those standards must be used until everything is worn 

 out. Perhaps it may be advisable in the end to adopt the metre, but it 

 is quite impossible in our time. I have shown you the importance here 

 of very small differences, but the most important of all, perhaps, is with 

 reference to screws. A perfect screw is one of the most important 

 things in mechanism, and it would be impossible to alter the distance 

 of the thread of our screws, otherwise I fully admit it would be a great 

 advantage to all countries if we could have only one measure, and I am 

 sure I would do anything I could to promote it. 



The CHAIRMAN : I am sure you will all agree with me in passing a - A*JAA A. 

 vote of thanks to Sir Joseph Whitvvorth, for his interesting communi- | 



cation. 



The vote of thanks was passed unanimously. 



The PRESIDENT : The next paper on our list is by Mr. Merrifield, 



ON SOLID MEASUREMENTS. 



Mr. C. W. MERRIFIELD, F.R.S. : I have been desired to give you an 

 account of solid measurement, and I must ask you to excuse any 

 shortcomings, by telling you that it was not until Monday that it was 

 proposed that I should undertake this task, and it was only yesterday 

 that I was aware I should have anything to say about fluid measure. 

 It has also been suggested to me that, besides solid measurement, I 

 should touch on a subject you have not yet had before you, which 

 would otherwise have been omitted from the programme, namely, 

 surface measurement. That necessarily precedes solid measurement, 

 because, unless a measure of solid contents be mere replacement or 

 displacement, we must first be able to measure the surfaces, and from 

 them only can we measure solids ; at least, that is the usual course 

 pursued by geometers, and the only course to which geometrical 

 measurement applies. I must first say a word or two with reference 

 to the accuracy of this measurement. The only tangible idea we 

 have of infinitesimals, and the only clear idea of a boundary is, to my 



