758 PROF. W. H. MILLER ON THE CONSTRUCTION OF THE NEW STANDARD POUND. 
liament on the 17th of June, 1824. In the fourth clause of this Act it is enacted, that 
the old troy pound of 1758, now in the custody of the Clerk of the House of Com- 
mons, shall continue to be the original unit or only standard of weight from which 
all other weights shall be derived; and that it is to be denominated ‘The Imperial 
Standard Troy Pound and that the avoirdupois pound, now in use, shall contain 
7000 grains, of which the troy pound contains 5760. In the sixth clause it is 
enacted, that if the standard troy pound should be lost or destroyed, it is to be 
restored by a reference to the weight of a cubic inch of distilled water, which has 
been found and is declared to be 252*458 troy grains, weighed in air with brass 
weights, at the temoerature of 62° Fahr., the barometer being at 30 inches. 
The Imperial standard troy pound was compared with five troy pounds of gun- 
metal, destined for the use of the Exchequer, the Royal Mint, and the cities of 
London, Edinburgh and Dublin, by Captain Kater in 1824 or 1825*. Denoting 
the standard troy pound by U, and the troy pounds of the Exchequer, the cities of 
London, Edinburgh, Dublin, and the Royal Mint, by Ex, L, Ed, D, RM respectively, 
it was found that 
No. of Comps. 
16 
12 
15 
18 
20 
grain. 
Ex =U + 0-0010 
L =U+0-0005 
Ed =U-0-0015 
D =U + 0-0022 
RM = U + 0-0021 
In the year 1829 the standard troy pound was compared with extraordinary care 
by Captain v. Nehus with two brass troy pounds and a platinum troy pound, all in 
the custody of Professor Schumacher, and with a platinum troy pound, the property 
of the Royal Society. 
Let Sb, K denote the two brass troy pounds, Sp the platinum troy pound in the 
custody of Professor Schumacher, RS the platinum troy pound the property of the 
Royal Society, t the temperature of the air in degrees of Fahrenheit’s scale, h the 
height of the mercury in the barometer in English inches, and reduced to the tem- 
perature of melting snow. Let A prefixed to the symbol of any weight denote the 
ratio of the density of the weight at the temperature of melting snow to the maximum 
density of water. The symbol placed between the symbols of two weights will be 
used to denote that they appear to be equal when weighed in air. The two weights 
in this case will not be equal unless their volumes are equal. When the weighings 
have been made in air of constant density, or have been reduced to what they would 
have been in air of given density ; or when, the volumes of the weights and the tem- 
perature and pressure of the air being unknown, we are compelled to assume the 
equality of their volumes, the symbol = may be substituted for 
* Philosophical Transactions for 1826, Part II. p. 18. 
