law/third_report_1821.pdf

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2 T H R-D E P O R OF THE COMMSSONERS f 1 APPONTED BY HS MAJEST CONS: DER ' THE S UBJECT WEGHTS AND MEASURES. Dated, London, 31 March Ordered, by The House of Commons, to be Priated, 5 April 1821.

3 THE APPENDX P. 5

4 T H R D OF THE COMMSSONERS Appointed by HS MAJESTY to consider the Subject of /.t WEGHTS AND MEASURES. -.,.. MAY.T,PLEASE YOUR MAJESTY, W E, the Commissioners appointed by Your MAJESTY, for the purof considering the subject of WEGHTS and MEASURES, - pose -- have now complet~exam~nat~on ot the Standa- we. have thought it necessary to compare. The Measurements'which we have lately performed, upon the apparatus employed by the late Sir George Shuckburgh Evelyn, have enabled us to determine, with sufficient precision, the weight of a given bulk of water, with a view to the fixing the magnitude of the Standard of Weight ; that of Length being already determined by the experiments related in our former Reports : And we have found by the computations, which will be detailed in the Appendix, that the weight of a cubic inch of distilled water, at 61' of Fahrenheit, is grains-of the Parliamentary Standard Pound of 1758, supposing to be weighed in a vacuum. We beg leave therefore finally to recommend, with all humility, to Your MA J E ST P, the adoption of the Regulations and Modifications suggested in our former Reports ; which are principally these : 1.-That the Parliamentary Standard Yard, made by Bird in 1760, be henceforwards considered as the authentic legal Stdndard of the British Empire ; and that it be identified by declaring, that inches of this standard, at the temperature of 6%" of Fahrenheit, have been rbund equal to the length of apendulum supposed to vibrate seconds in London, on the level of the sea, and in a vacuum That

5 4 -THRD REPORT OF THE COMMSSONERS 8.-That the Parliamentary Standard Troy Pound, according to the two pound weight made in 1758, remain unaltered; and that Troy Grains be declared to constitute an Avoirdupois Pound ; the cubic inch of distilled water being found to weigh at 62", in a vacuum, Parliamentary grains That the Ale and Corn Gallon be restored to their original equality, by taking, for the statutable common Gallon of the British Empire, a mean value, such that a gallon of common water may weigh 1 o pounds avoirdupois in ordinary circumstances, its content being nearly cubic inches ; and that correct Standards of this MPXRAL GALLON, and of the Bushel, Peck, Quart and Pint, derive'cl from it, and of their. parts, be procured without delay for the Exchequer, and for such other pffices in Your Majesty's &lcrmilaions, as may be judged.most conv.en,ient for the ready use of Your Majesty's subjects. 4.-Whether any further Legislative enactments are required, for enforcing a uniformity of practice throughout the British Empire, we do not feel ourselves competent to determine. But it appears to us, that; nothing would be more conducive to the attainment of this end, than to increase, as far as possible, the facility of a ready recurrence to the legal Standards, which we apprehend to be in a great measure attainable by the means that we have recommended ; it would also, in all probability, be of advantage to give a greater degree of publicity to the Appendix of our last Repnrt, rnntaining a cornpar~~oa of ~lic measures employed throughout the country; cualu~ua~-y 5.-We are net aware that any further services remain for us to perform, in the executian of the Commands laid upon us by Your Majesty's Commission : But, if any superintendence of the Regulations to be adopted were thought necessary, we should still be ready to undertake such nspections and Examinations, as might be required for the complete attainment of the objects in question. London, 31 March (Signed) GEORGE CLERK. DAVES GLBERT. Wx H. WOLLASTON. THOMAS YOUNG. HENRY KATEB,

6 ON WEGHTS AND MEASURES. APPEN HE Commissioners having been furnished, by the kindness of the T Honourable Charles C. C. Jenkinson, with the apparatus employed by the late Sir George Shuckburgh gvelyn, in the determination of the magnitude of tlle standard weights, and there being some doubt of the perfect accuracy of his method of measuring the capacity of the bodies employed, it was judged necessary to repeat that Measurement with greater precautions ; and the resrilts of Captain Kater's experiments have afforded some slight corrections of the capacities in question. - The sides of Sir George Shuckburgh's cube were found by Captain Kater equal to , and inches ; the diameter of the cylinder , and its length inches ; and the diameter of the sphere inches. Hence the content of the cube appears to be i=?$~&%g~~at T5FtTie cyllnder ;-here inches of Bird's Parliamentary Standard of 1760, recommended in the last Report of the Commissioners, or of the Standard made by Troughton for Sir George Shuckburgh. The difference of the weight of the cube in air at 62", with the barometer at 2i.0, and in water at 60.2", was grains; and, adding to this the weicht - of an equal bulk of the air at 62", wl~ich is =+.% of that of the water, or grains, and subtracting from it,fs of this, or 4.26 grains, the buoyancy of the brass weights, we obtain grains for the weight of the cube of water in a vacuum at 60.2'. Now this cube is less than the supposed measure at the standard temperature of 62", in the ratio of 1 to.oooo567, on account of the contraction of the brass; and the water is denser than at the standard temperature, according to Mr. Ciilpin's experiments, in the ratio of to.99981, or of to 1, the whole correction, for the difference of 1.8"~ being, , or 3.55 grains, making for the weight of the cube of water in a vacuum at 62"; which, t ivided by ~, gives for the weight of a cubic inch in Sir George Shuckburgh's grains. n the same n-lanner, we obtain for the cylinder, which was weighed in air under the same cil-cumstances, and in water at GO.~", the digerence being 1 <)oo(i.s.; grains, tl~ecorrection &.-$:-. ;: for the effect of buoyancy, amounting to 9.43 grain, ; and for the diitizrence of temperature of tlie water and braas conjointly, the densities being and.gggs~o, 3 &3. B the

7 6' THRD REPORT ON WEGHTS AND MEASURES. the correction =.ooo095, or.so grains,leaving grains for the whole correction of the weight, as reduced to a vacuum at 62O, and making it , which divided by , the content of the cylinder, affords us for the cubic inch in a vacuum at 62O. The sphere was weighed in air at 679 the barometer standing at 29.74; the correction for buoyancy is here '2. 2~.-&, or for grains, ; while the temperature of 66" requites, for the dserence between the expansion of brass and water, the addition of.ooo42 --,000126, or of the whole, that is f 8.43 grains, making the wholc correction 38.1 j, and the weight in a vacuum ; which, divided by J , gives us , for the cubic inch in a vacuum. The Mean of these three Measures is , giving for the three errors +.o 19, w.037, and +.O g ; and this Mean, reduced to the Parliamentary Standard, makes grains, for the cubic inch of distilled water at 62", weighed in a vacuum, or in air, under the common circumstances of the atmosphere, when weights of brass are employed. n a vacuumtat the maximum of density, that is at 3g0, the weight of a true cubic inch will be 2.53 grains, and of a cubic decimetre 15440". The proposed mperial Gallon, of ten pounds, or grains, of water, will contain verv nearly cubic inches, under common circumstances. [ * l' appears, however, from an official Report, obligingly communicated to us hy lr. Kelly, that the actual standard chiliogramme -has bccn found ta contain only English grains.1