802 PROF. W. H. MILLER ON THE CONSTRUCTION OF THE NEW STANDARD POUND.

has returned it, though I cannot find it amongst my papers. Even if you hadNehus’s original drawing you would not be able to find the volume, the only heighthe has measured being that of the whole pound. The heights of the points a, b, c areonly found by holding a scale in a vertical position near the pound. The diameterson the contrary are measured.”

By a comparison of the figure of U with a profile of V traced mechanically, andwith careful measurements of its axis and diameters, the axis and the extremediameters of the knob and cylindrical portion of U appear to be a very littlegreater than the corresponding dimensions of V, the differences in other parts beingexactly where we might expect the drawing to be inaccurate from the manner inwhich it was made. (In the figures of the weights V, O, M, B, the dotted line isthe profile of U.) The diameters and axis of U being measured with a bow-leggedcompass, were more likely to err in excess than in defect. Making every allowancefor this, it did not seem possible, on looking at the profiles of U and V, to supposethat the volume of U was less than that of V. But the volume of O, as well as thatof M, being less than that of V, it appeared that of the three weights V, O, M,V approximated most nearly to U in volume. As the. existing data were utterlyinsufficient to determine how much, if at all, U exceeded V in volume, it appearedsafest to assume the volumes of U and V to have been equal. This course wasrecommended also by Professor Schumacher in his letter of October 3, 1843.

Long after this resolution had been taken and acted upon, and the new standardconstructed in accordance therewith,the troy pound O came by purchase into the handsof the Committee. The surface of O was studded with numerous small pores, show-ing it to be an extremely bad casting. It was only after repeatedly boiling the waterin which it was suspended that the air-bubbles which attached themselves to the poresceased to appear. It was weighed in water April 2, and then left to dry till April 28,when on being weighed in air it appeared to be about 16 grains too heavy. By heat-ing it to above the boiling-point, the water that had been retained in the cavities wasexpelled, and the weight reduced to 5759-83 grains. Afterwards, by placing it in ajar containing water, under the receiver of an air-pump, and alternately exhaustingthe receiver and boiling the water, the cavities communicating with the surface werefound capable of containing 21-37 grains of water. This explains the seeming para-dox, that although the linear dimensions of O are hardly less than those of V, andsensibly greater than those of M and B, its specific gravity is considerably greaterthan that of V, and slightly exceeds that of either M or B.

Of the weights used in the following weighings, those marked (100), (200), (400)...,of nearly 100, 200, 400 ... grains respectively, are of bronze, for which log A—0'92260.The smaller weights are of platinum. By a mean of four observations, April 30,1853,

0*(3200) + (1600) + (800) + (100) + (32) + (16) + (8) + (4) —0*1360 grain in air(D= 12, C=12'2, F= 756-4, E=1P8).

0^5699-9704 grains of bronze -f-59'8607 grains of platinum in air (£=12-1,*=755-4).