766 



SCIENCE. 



[N. S. Vol. III. No. 73. 



thirsty traveller, otlier than a mathema- 

 tician, ever ask for a third of a quart of beer ? 

 It may be taken as a practical result of nat- 

 ural selection, permanent through thous- 

 ands of years, that halves and quarters of 

 the ordinary unit for any class of measure- 

 ment are natural and convenient. 



" In the metric S3'stem we find the kilo- 

 gramme, half-kilogramme and quarter-kilo- 

 gramme continually used in weighing. 

 There is no obligation to always call the 

 half-kilogramme 500 grammes, or the quar- 

 ter-kilogramme 250 grammes. For smaller 

 quantities the gramme is a thoroughly con- 

 venient measure. For distances travelled 

 we have the kilometre, half-kilometre and 

 quarter-kilometre. For measuring cloths, 

 ribands and tapes, in retail shops, we have 

 the metre and centimetre, which are thor- 

 oughly convenient and popular for all or- 

 dinary use. The centimetre (about four- 

 tenths of an inch) is a thoroughly con- 

 venient smallest unit for most practical pur- 

 poses; and for finer measurements the 

 workman under the metric system has a 

 great advantage in the millimetre and half 

 or quarter millimetre over the British work- 

 man with his troublesome and fatiguing 

 eighths, sixteenths, thirty-seconds and six- 

 ty-fourths of an inch. 



" The great advantage of the metric sys- 

 tem is its uniform simplicity, all measure- 

 ments of length, area, A^olume and weight 

 being founded primarilj'- on the kilometre. 

 The kilometre is very convenient for meas- 

 uring great distances on the earth's surface, 

 because a journey a quarter round the world 

 is nearly enough 10,000 kilometres for al- 

 most all practical purposes. If our travel- 

 ling was habitually, not on the earth's sur- 

 face, but along diameters through the cen- 

 tre, there would be some practical value in 

 the merit discovered for the British inch by 

 Sir John Hersohel that it is approximately 

 one one-hundred-millionth of a diameter of 

 the earth. 



" The thousandth of the French ton is 

 the kilogramme ; and the cubic decimetre, 

 or the thousandth of the cubic metre, is the 

 litre, which is the common popular unit for 

 liquid measui'C ; so that any one who has 

 correct weights can verify for himself his 

 litres or other measures for liquid. This 

 particular merit of themetricsystem, which, 

 so far as I know, has not been much, if at 

 all, noticed by your correspondents, is of 

 very great importance in mechanics and 

 engineering. In virtue of it the weight of 

 any quantity of material is found in tons, or 

 in kilogrammes, or in gi-ammes, simply by 

 multiplying its volume in cubic metres, or 

 in cubic decimetres, or in cubic centimetres, 

 by its specific gravity ; and thus a very 

 great deal of labor which is entailed upon 

 mechanical engineers, civil engineers and 

 surveyors in England under the present 

 system will be done away with when the 

 metric system comes into use. 



" But now, considering the wants and the 

 convenience of the whole population, think 

 of the vast contrast between the practically 

 valuable simplicity of the metric system and 

 the truly monstrous complexity of British 

 measurements in miles, furlongs, chains, 

 poles, yards, feet, inches; square miles, 

 acres, square yards, square feet, square 

 inches: cubic yards, gallons, quarts, pints, 

 gills ; tons, hundredweights, quarters, 

 stones, pounds, avoirdupois (7,000 grains), 

 ounces avoirdupois (437"5 grains), drams 

 avoirdupois (27-34375 grains), pounds troy 

 (5,760 grains), ounces troy (480 grains), 

 drams apothecaries' (60 grains), &c. Look- 

 ing at the question from all sides, and con- 

 sidering all the circumstances, I believe it 

 will be found that the thorough introduc- 

 tion of the metric system, for general use 

 in Great Britain, will be beneficial to all 

 classes; and that the benefit will, in the 

 course of a few weeks, be found to more 

 than compensate any trouble involved in 

 making the change." 



