794 PROF.W. H. MILLER ON THE CONSTRUCTION OF THE NEW STANDARD POUND. 
upright stroke of the 5 in the type appears to have been broken off, and the defect 
supplied in the inscription by a cut with a chisel. The letters SF are impressed dia- 
metrically opposite to the T. This weight, as well as the others of the same date, 
is of one piece of metal, without any cavity for adjustment by the addition of bits 
of wire. Mr. Simms, to whom it was shown, pronounced it to be of soft gun-rnetal, 
as hard as cast brass, but not so hard as hammered brass, and, for such an alloy, a 
very bad casting. 
As the balance ordered of Mr. Barrow was not yet ready, Mr. Vandome’s troy 
pound (V) was weighed in water with a balance of 10^ inches beam by Robinson. 
The case of this was too small to admit a large cylinder of water, the use of which is 
considered essential to the accuracy of observations of this kind, and some unaccount- 
able discordances in the weighings of V in air impair the probable accuracy of the 
result. For these reasons the result alone is given, omitting the details of the obser- 
vations. By a mean of six weighings in water in July and August, 1843, the density 
of V at 0° C. appeared to be 8*15105 times the maximum density of water. This 
value, notwithstanding its uncertainty, was sufficiently exact for a preliminary com- 
parison of the densities of the weights made in 1758. The accurate determination of 
the density of V and of the other weights of the same date presents considerable 
difficulty; for the pores in the metal are so deep, that the complete expulsion of 
the air contained in them is very questionable, even after prolonged immersion in 
boiling water. 
The following observations were made with Barrow’s balance under circumstances 
more favourable to accuracy. The glass jar containing the distilled water in which 
V was weighed, was 6*7 inches in diameter and 6*5 inches deep. V was suspended, 
from the pan of the balance, by a hook attached to a fine copper wire, 7’5 inches 
of which weighed about one grain. In order to expel the air adhering in bubbles 
to the weight, or contained in the cavities in the metal, it was placed, with the fine 
wire attached to it, in water in a bell-shaped jar of thin glass, just large enough to 
contain the weight. The jar was suspended over the flame of a spirit-lamp by a stout 
wire bent at its lower end into a ring into which the jar descended to its rim, and the 
water allowed to boil till it was supposed that the air was entirely expelled. The 
small jar containing the weight was then immersed in the water which very nearly 
filled the large jar, the suspending wire hooked on to the under side of the scale pan, 
and the small jar lowered till the weight hung clear of it, and then removed. The 
transfer of the weight from the small jar to the large one was thus effected without 
taking it out of the water. The counterpoise was placed in the left-hand pan of the 
balance; V was suspended in water from the right-hand pan. Small weights were 
placed in the right-hand pan till equilibrium was produced, and the readings of the 
scale observed. V was then removed, leaving the hook suspended in water, and a 
volume of water equal to that ofV added to the water in the jar ; the weights A, B, C, D, 
&c. were placed in the right-hand pan till equilibrium was again produced, and the 
