108 Transactions. — Miscellaneous. 



In like manner the theoretical kilogramme and litre of the French 

 are decimally referred to their theoretical metre on their own peculiar con- 

 ventions as to the mode of weighing. 



This premised — (1) The Imperial foot is to the geometrical in the 

 exact proportion of 999 to 1,000, a relation numerically so exact that it 

 may fairly be considered as mathematical ; and (2) and (3) the Imperial 

 half-pint and ounce are, each of them, to its geometrical prototype as 

 2,600 to 2,601. 



Turn we now to the practical deviations from their theoretical ideals 

 in the case of the French units. Here again (1) the practical metre is 

 shorter than its theoretical ideal. The approximation is, indeed, closer, 

 but the point of real importance is the extreme numerical simplicity of the 

 relation in our case, more easily borne in mind and more readily calcu- 

 lated on in any proposed case. (2 and 3) Any error in the practical 

 value of the metre entails a triple amount of aliquot error on the practical 

 kilogramme and litre, so that in the cases of these units the proportion 

 between their practical and theoretical values is not that of 6,400 to 6,401, 

 but of 2,133 to 2,134. Here, then, the greater degree of approximation is 

 in our favour ; and it is to be observed that in our case this triplication of 

 error does not hold good, since by a happy accident our standard pound 

 has been fixed quite independently of our standard yard, and our gallon is 

 defined as 10 pounds of water. 



Like all other terrestrial things, the earth's axis is doubt- 

 less subject to minute secular changes ; but it is at least a 

 right line, and a line of unique significance, as it is used by 

 astronomers as the unit-measure for distances within the 

 solar system. It is therefore very convenient that it should 

 harmonize with our ordinary standards. Moreover, its length 

 — five hundred million inches — is a consistent decimal rela- 

 tion, which the forty million metres of the French system is 

 not. "Was it, however, by a mere "happy accident" that 

 such remarkable concordances occurred ? I have more faith 

 in both the knowledge and wisdom of the men who devised 

 them of old than to think so. Astronomically and mathe- 

 matically, the self-complacent French scientists of a hundred 

 years ago were as babes compared with the architect of the 

 Pyramid. 



Sir John Herschel's casual reference to the " peculiar con- 

 ventions" of the French method brings out another instance 

 of the practical nature of our system as contrasted with the 

 artificial and doctrinaire methods of the metric system. 

 British observations and tests are made under reasonable and 

 normal conditions of atmospheric pressure and temperature. 

 The French observations have to be corrected to the prac- 

 tically impossible conditions of sea-level and the freezing- 

 point of water. 



The British people are free to use, and do habitually use, 

 decimal divisions of their own standards wherever such 

 division is found to be right and convenient. Any instru- 

 ment-dealer will supply rules graded into eighths, tenths, or 

 twelfths, as desired. Foreigners are nob so ignorant of our 

 standards as the metric advocates would have us believe. 



