iS'/A' WILLIAM SIEMENS, F.R.S. 



305 



In the tU*-us$ion of the Paper 



"OX THE RELATIVE ADVANTAGES OF THE INCH 

 AND THE METRE AS THE STANDARD UNIT 

 OF DECIMAL MEASURE," by MR. JOHN FBI; 

 of Leeds, 



MR. C. W. SIEMENS * said he had paid some attention to the 

 subject of the metre system, and had carried out a good deal of 

 work iii France with the metre scale, but had not found any 

 inconvenience in working upon that system. His own draughts- 

 men easily fell into the habit of working with the metre scale, and 

 he had had frequent opportunities of watching its working in 

 the hands of French workmen. There was one misconception 

 frequently entertained in this country with regard to the metre, 

 namely that as the metre was the basis of the system it must 

 necessarily be taken as the unit of measure in all instances. This 

 was not at all the case in France however, where, although the 

 metre was the basis of the system, the millimetre was really the 

 unit in mechanical engineering, and mechanical drawings were 

 figured not in metres but in millimetres. He found the millimetre 

 was a very convenient unit for setting out small mechanical work ; 

 for being equal to about l-25th inch it was smaller than l-16th inch 

 and larger than l-32nd inch, and was therefore just such a 

 dimension as a workman could still readily appreciate in following 

 a drawing. Of course the millimetre without further subdivision 

 would not suffice to measure with such wonderful precision as was 

 attained by Mr. Whitworth's system of contact measurement, 

 which had been carried out in connection with the inch divided 

 decimally. But for such accurate measurements the unit of 

 measure employed was of little consequence, since any unit could 

 be decimally subdivided to such an extent as to give the required 

 degree of accuracy ; and under the metre system the millimetre 

 was subdivided for the very minutest descriptions of work into 

 100 parts caljed centiemes, each of which was equal to about 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineer*, 

 1865, pp. 42-44. 

 VOL. II. 



