Mr Sang on the Flexure of Thin Bars. 321 



a potable beverage, fair, on the whole, as this may be, M. Du- 

 pasquier expresses his ardent desire that the project, alluded 

 to at the commencement of this paper, of introducing these 

 springs by means of an aqueduct, which would supply the 

 wells of Lyons, might be carried into execution ; for he con- 

 siders the scheme as highly calculated both to improve and 

 corroborate the health of all classes of his fellow-citizens, and 

 also to contribute greatly to the maintaining of the reputation 

 and advancing the superiority of their valuable manufactures. 



On an Erroneous Deduction drawn by the late Captain Henry 

 Kxter fro?n his Experiment on the Flexure of Thin Bars. 

 By Edward Sang, Esq. Actuary, Edinburgh, M. S. A. 

 Communicated by the Society of Arts for Scotland.* 



In June 1830, Captain Kater read before the Royal So- 

 ciety of London a paper on the Error in Standards of Linear 

 Measure, arising from the thickness of the bar on which they 

 are traced. This error he states to have been discovered by 

 him during the adjustment and verification of the copies of 

 the imperial standard yard destined for the Exchequer, Guild 

 hall, Dublin and Edinburgh ; and he also states his belief, that 

 the source of this error was previously wholly unsuspected. 



On perusing the paper, it is found that the error in ques- 

 tion arises, not from the thickness of the bar, but from its 

 flexure or change of shape ; and, with all due deference to the 

 authority of Captain Kater, and the silence of the Royal So- 

 ciety of London, it is my distinct conviction that the change 

 of dimension induced by mechanical agency was known very 

 long ago, and particularly, that the very amount of change in 

 the case before us could have been computed beforehand by 

 help of formula? known since the days of the Bernouillis. 

 The anachronism of the discovery, however, is not that point 

 to which I wish to draw the attention of the Society of Arts : 

 I notice it merely because its occurrence may serve to explain 



* licad before the Society of Arts for Scotland, 8th February 1841. 



