Older than the Arago kilogram is the °com mittee meter,* as it has been called, which me given to Mr. F. R. Hassler, later superinind ent of the Coast Survey, by J. F. Tralle a. deputy from the Helvetic Republic in the emt mince charged with providing for the prod"• tion of the metric standards in 1799. It brought by Mr. Hassler to the United Sott in 1805, and was a short time later donated' him to the Philosophical Society of Philadelpil Not long afterward, when Mr. Hassler t-i• up the Coast Survey work, the sOdi-ey placed this standard at his disposal, and until 1890 it served as the standard for the determinations made by the survey. This meter is made of iron, and is marked with the stamp of the com mittee, which was a small ellipse, having three quadrants shaded, the remaining one bearing the figures 14000,000, that of the number of meters in a quadrant of the earth's meridian.
Almost a half century elapsed after the pro posal of a metric conference by John Quincy Adams before this project was realized. On 1 Sept. 1869, a decree of Napoleon III summoned an international conference to provide for the production of new and absolutely exact metric standards of mass and length. Fifteen nations responded to this invitation, and the delegates assembled in Paris, 8 Aug. 1870. In spite of the fearful disasters of the French armies and the consequent rapid invasion of French terri tory by the Germans, five meetings were held before the conference was forced to disband. The following were the 15 countries accepting the invitation of the French government to send representatives to this first Paris con ference, of August 1870: Austria, Ecuador,• France, Great Britain, Greece, Italy, Norway, Peru, Portugal, Russia, Spain, Switzerland, Turkey, United States, Colombia.
The project was not abandoned, however, and a second conference was called two years later, under the Third Republic, and repre sentatives of 30 nations assembled in Paris on 24 Sept. 1872, remaining in session until 12 Oc tober of that year. Their deliberations resulted in the adoption of 40 resolutions bearing on the construction of the new standards; of these 21 especially applied to the meter and 12 to the kilogram, the remainder referring to various details of the plan to be pursued, and to the precautions to be taken for the preservation of the standards when produced, as well as for the maintenance of their invariability. A most important point was the exact determination of the alloy to be employed, and the eventual decision was that it should be one of 90 cent platinum and 10 per cent iridium, a toler ance of 2 per cent in excess or deficiency be ing permitted. This alloy possessed at once a high degree of hardness and of resistance to chemical action, and also was susceptible of re ceiving an exceedingly fine finish. A main share in the task of ensuring the production of a thoroughly satisfactory amalgamation of the metals was entrusted to the chemist, Henri Sainte-Claire Deville. The first ingot made had a weight of 238 kilograms and is commonly known as the °alloy of 1874," from the year in which it was produced. This alloy, however, did not meet with the approval of the commis sion, although several standards were made out of it to test its qualities. It was now determined to have recourse to the skill and experience of the great London firm of platinum refiners, Messrs. Johnson, Matthey and Company, and
as a result of patient effort they were finally able to offer a casting which was found by the chemists of the International Commission, and by those of the French section, to exceed the requirments; from it were made 31 prototype meters and 40 kilogram weights. The meters were sent, early in 1::7, to the International Bureau to be compared with the °metre des Archives" and also with one another. By 1889 this task had been accomplished, and on 26 September of that year the work of the In ternational Committee received the approval of a general conference assembled at Paris. The meter and the kilogram found to be in closest agreement with the meter and kilogram of the Archives were denominated the °In ternational Meter,* and the °International KilKilo gram," and were deposited at the International au of Weights and Measures, in a vault provided' with three separate locks, the keys to which are in the possession, respectively, of the Custodian of the Archives of France, the presi dent of the International Committee and the director of the International Bureau. This vault must not be opened oftener than once in a year, and in the presence of the three officers to whom the keys have been confided. To each of the contributing countries were given two of each of the new standards, which were all accompanied by attested certificates of compari son, two hard glass thermometers, each of which had a table of corrections in terms referring to the hydrogen scale, and a piece of the alloy cut from the end of the bar and destined to be used in testing the coefficient of expansion; each kilogram had a rock-crystal bedplate and other requisites for its safe conveyance. The meters allotted to the United States, Nos. 21 and 27, bore corrections of +2.5 microns and —1.6 microns, respectively; the probable error of the determinations being estimated, as a result of 784 individual comparisons, at less than 02 microns. The two kilograms assigned were numbered 4 and 20, and had corrections in weight of —0.075 and 0.039 milligrams, and in voluttie of 46.418 and 46.402 milliliters, respect ively. Here from 1,092 individual weighings the error of the determination is less than 0.002 milligrams. Meter No. 27 and Kilogram No. 20 were carefully packed and brought to this country under seal by George Davidson of the Coast and Geodetic Survey. On 2 Jan. 1890, President Harrison received them at the Execu tive Mansion. The seals were broken in his presence, and he gave a certificate to the effect that they had been received in good condition, and that he was fully persuaded they were the standards to which the report referred. The other kilogram and meter were received in July 1890, and were deposited in the Office of Weights and Measures where the meter and kilo gram recognized by the President as national standards had already been placed. By a de cision made by the superintendent of weights and measures, on 5 April 1893, and approved by the Secretary of the Treasury, the interna tional meter and kilogram were made the funda mental standards of length and mass in the United States, this applying to the customary weights and measures as well as to those based on the metric units. The standards passed under the control of the Bureau of Standards on its establishment 1 July 1901, pursuant to the provisions of the act of 3 March 1901.