THE SCIENTIFIC PAPERS OF 



l-2500th inch, and was therefore as suitable for very small 

 measurements as the thousandth of an inch. 



Moreover independent of the metre being so convenient a measure 

 for ordinary commercial purposes and already so extensively adopted, 

 he thought it deserved serious consideration whether it would be 

 wise to abandon altogether a measure of some such length as the 

 yard or the metre, as would be the case if the inch were taken as 

 the unit of measure. He agreed that in respect to its verification 

 the metre was not an absolute length ; but that was really not 

 a matter of consequence, since, if the quadrant of the earth's 

 circumference were measured a hundred times, each measurement 

 would be likely to differ from all the rest ; and if the measurement 

 were taken several hundred years hence, perhaps the earth itself 

 would have slightly altered in size during that period. The 

 verification of the- metre was therefore dependent upon the accuracy 

 of copying an original standard, just the same as in the case of 

 verifying the inch ; and this original standard would always be 

 referred to, instead of measuring the quadrant of the earth over 

 again. It was nevertheless of some importance that the unit of 

 length should be a measure referable to the size of the earth, because 

 it was then easily applied to geographical and even astronomical 

 purposes ; and in this respect the metre had an advantage as the 

 unit of length, in being approximately an even decimal sub- 

 division of the quadrant of the earth's circumference. 



He concurred entirely in the desirability of having a system of 

 measure in which there should be a direct decimal relation between 

 linear, square, and cubic measure, and between these and weight, 

 as had been explained to be the case under the metre system. It 

 had been correctly explained that the metre afforded a very great 

 facility for ascertaining the weight of any bulk of material, its 

 linear dimensions and specific gravity being known. There was 

 then the least demand made upon the memory, since the specific 

 gravity of different substances was all that had to be borne 

 in mind, instead of a number of practical rules having to be 

 recollected, which were applicable to one material only. The 

 product of the cubic dimensions of any substance in metres 

 multiplied by its specific gravity gave the weight of the substance 

 in tonnes, being almost identical with English tons, or in kilo- 

 grammes when the decimal point had been shifted three places to 



