=The Metric System= (a Letter to the London Times).--SIR: I see that on Wednesday next, the 22d inst., the President of the Board of Trade is to receive a deputation from the Decimal Associations and others to urge on the Government, not merely the adoption of the decimal system of notation, but the compulsory application within two years of the metric system of weights and measures in its entirety. I have been hoping to see a letter in the Times from some person of importance calling attention to this deputation. I fervently trusted I should notice one from your correspondent, Mr. Herbert Spencer, who, a year or so back, contributed a series of thoroughly well-thought-out and logical articles, exposing the fallacy of the metric system; but if any such letter has appeared I have, unfortunately, missed it. I believe this agitation to be largely due to scientific professors who have been brought up on foreign books, and have found it too much trouble to convert foreign measurements into English; further, due to the promptings of a number of foreign merchants, forming (happily, or unhappily) now so large a portion of our traders-men who, also, do not wish to take the trouble of converting foreign weights and measures into English. As regards the suggestion, made time after time, that the metric system is one giving the greatest simplicity to calculations, I say unhesitatingly, from very considerable experience, that it is one absolutely subversive of mental arithmetic, and I appeal to anybody who has ever had the misfortune to wait at the _guichet_ of a French railway station while the clerk inside has been calculating the total amount to be paid for two first-class and one second-class from "A" to "B" with a piece of chalk, or pencil and paper, to compare the speed and the certainty of this process with the answer that he would get at Euston, or at any such station in Great Britain, and say which system shows by results the advantages in point of time and in accuracy. The French themselves, as has been pointed out on more than one occasion, find the metric system too irksome, and they evade it. According to the metric system, one of its great merits is that you can state every required quantity by multiples or submultiples of ten--metre, 1; decimetre, 0.1; centimetre, 0.01; millimetre, 0.001. But no Frenchman thinks of expressing himself in this way. Instead of 0.01, he says cm. 1. For a millimetre, he says mm. 1. When he comes to large weights, does he not commonly abjure the 1,000 kilos and write one tonne? When he comes to domestic weights the kilogramme is found too large; the half of this, the practical equivalent of the pound, is wanted. He ought to write 500 grammes. He does not. He abjures his decimals, and writes one half kilo. But I feel I must not take up your space by multiplying instances, so well known to many who have studied the subject, of the unbearable burden of the decimal _plus_ metrical system compulsorily carried out.