THE METRIC SYSTEM OF WEIGHTS AND MEASURES 

 AND THE DECIMALISATION OF THE COINAGE. 



Bv RoBKKT Thorbukn Avton Inn'es. F.R.A.S.. F.R.S.E. 



The metric system is the most important decimal system, 

 and it is more than a mere decimal system ; it is a system in which 

 measures of weight, length, area, and capacity are all simply 

 interrelated. 



In the Journal of ihe Koyal Society of Arts. No. 3.293, of 

 31st Decemher. 191 5, Colonel Sir Charles M. Watson makes a 

 spirited defence of the English measures of length which in his 

 last paragraph he claims to be prehistoric. Now, there is a good 

 deal to be said for our inch, foot, yard, and mile, cumbersomely 

 as they are related to each other. But too nuich should not be 

 said. The English acre has no obvious or indeed simple relation 

 to any one of them. The side of an acre square is 22 V 10 yards, 

 which is a bad coordination. But if we gave way on measures of 

 length, what about those of capacity and weight? That is just 

 it I \\'e have to learn three distinct systems, not one of which 

 is in the decimal notation or any other notation, but a mixture. 

 W'e may learn these systems, but they are so artificial that unless 

 we use them regularly, we must perforce forget them. 



In practice I find a millimetre a very convenience starting 

 j)oint, and for mental estimation I remember 2^ millimetres 

 ( 25 mm. ) are e(|ual to tiie length of the middle bone of my 

 little finger, or about an inch, and that a metre is roughly equal 

 to a yard, and is j,ooo mm. A millimetre is the smallest distance 

 which can be conveniently or easily seen by the eye. ( )ne can 

 \isualise a \ard or a metre, but I do not think that without actu- 

 al) \' measuring anyone could distinguish between a yard and a 

 metre length if shown individually. 



A cubic metre of water weights a ton (a metric ton), which 

 is subdivided into 1,000 kilograms. A metric ton is equal to 

 2,200 lbs., an bjiglish ton to 2,240 lbs, and a short ton( such as- 

 our ton of .coal in South .Xfrica), 2,000 lbs. But the especial 

 jioint to notice is that a cubic metre of water weighs a ton, because 

 this being so. a cubic metre of anything else weighs its specific 

 gravity in tons. What simplicity ! The specific gravity of iron 

 is 7.8, therefore a cubic metre of iron weighs 7.8 tons, cr 7 t'>!"* 

 800 kilograms. 'I'he specific gravity of oak or beech is about 0.75, 

 therefore a cubic metre weighs three-(|uarters of a ton. or 750 

 kilograms. 



For li(|uids measures of capacity are generallv used, and 

 ca])acities differ, although some liquids should be and are now 

 sold by weight, such as sulphuric acid. In hjiglish measure we 

 have — 



