In Coast Survey report for 1876, J. E. Hilgard calls attention to another difficulty in the matter of extreme accuracy, in the uncertainty with regard to the permanence in the length of a bar, and states that the bronze standard bar No. 11 and the Low Moor iron standard bar No. 57, presented to the United States by Great Britain, are found to have changed their relative length by 0·00025 inch in 25 years; the bronze bar being now relatively shorter by that amount. This subject, he states, is undergoing further investigation. COMPARISON OF UNITED STATES AND FRENCH STANDARDS. In 1817 Mr. Hassler examined the French standards in America, for the Coast Survey, using the Troughton bronze standard scale, which is identical with Sir George Schuckburg’s standard, as the reference, with the following results, all being reduced to temperature of 32° F. Original Iron Mètre, 1799 39·381022708 inches. Lenoir Iron Mètre, Coast Survey 39·37972015 “ “ Brass “ “ 39·380247972 “ “ “ “ Eng. Dept. 39·38052739 “ Canivet Iron Toise, 1768 76·74334472 “ Lenoir “ “ 76·74192710 “ In 1814 Troughton had compared with his own scale in London two of the above. Lenoir Iron Mètre, C. S. 39·3802506 inches. “ Brass “ “ 39·3803333 “ In 1832, under resolution of Congress, Hassler again compared the French standards in the United States, using as before the Troughton scale, and reducing all to temperature of 32° F. as follows: Original Iron Mètre, 1799 39·3808643 inches. Lenoir “ “ C. S. 39·3799120 “ “ Brass Mètre C. S. 39·380447 “ “ “ Eng. Dept. 39·3801714 “ “ “ “ in 1829 39·3807095 “ Fortin “ State Dept. 39·3796084 “ “ Treas. “ 39·3795983 “ Iron Mètre “ “ 39·3807827 “ Gilbert “ Univ. of Virg. 39·365408 “ Platinum Mètre 39·3803278 “ “ (Nicollet) 39·380511 “ Canivet Iron Toise, 1768 76·74290511 “ Lenoir “ 1799 76·74047599 “ From the mean of his comparisons between the United States brass Troughton standard yard and the authentic French standard mètres used by the Coast Survey, Hassler, in 1832, deduced the value of the mètre at 39·3809172 inches, at 32° F., and by correction for expansion to United States standard temperature of 62° F., he made the mètre at 32° equal to 39·36850154 inches at 62° F.