28 APRIL 1866, Page 13

[To THE EDITOR OF THE " SPECTATOR."] Lauderdale House, Highgate,

April 21, 1866. SIR,—I am very happy to find that Mr. Sonnenschein has entered on the discussion of the merits of the Metric system of measures and weights, as well as of the " difficulties and costa of the pro- posed change." But I wish to correct some errors in his letter which appears in the Spectator of this morning.

1. He calls the meeting held on the 23rd ult. a meeting of the " Metrical Society." There is no society having this designation and aiming at any object supposed in Mr. Sonnenachein's letter. The meeting was called by the Council of the International Decimal Association and the Metric Committee of the British Association for the Advancement of Science, with a view to con- sider the advantages of the metric system of measures and weights, and the best methods of introducing that system through the agency of education.

2. He argues on the assumption that one object of the meeting was to oppose in some way the use of the sovereign, or, as he calls it, "the English twenty-shilling piece," whereas the meeting was not intended by its promoters to refer at all to the subject of money or coinage.

3. He objects to the unit of the metric system as " a very fan- ciful, and not an absolutely correct one." The original metre, from which all other metres have been taken, is the bar of platinum deposited by the French Government in their archives on the 22nd of June, 1799. Mr. Sonnenschein truly states that its length is " very nearly one ten-millionth part of the distance from the North Pole to the Equator." Its inventors did not pretend to greater correctness than this, well knowing that absolute accuracy in the measure of the earth was impossible. Its very near ap- proach to accuracy was, however, an acknowledged proof of their transcendent skill. It has answered its intended purpose, and has proved an inestimable blessing to mankind.

With these three exceptions, your correspondent's observations appear to me to be correct, and I shall wait with great interest for the further remarks of so able and experienced a writer.