876 PROF.W. H, MILLER ON THE CONSTRUCTION OF THE NEW STANDARD POUND. 
tained. From M. Letronne and M.Lallemand, Officers of the Archives, to the 
latter of whom the custody of the standards was confided, I received every possible 
assistance. The balance was mounted on a strong and heavy carpenter’s bench in a 
room paved with brick, on the ground floor of the Archives. On unpacking the 
stereometer, the graduated tube was found to be broken, in consequence, as 
M. Bunten affirmed, of mere contact with a slender iron wire used in cleaning the 
tube with cotton wool, and left in it in ignorance of the peculiar action of iron wire 
on the interior of a glass tube, and not from any violent shock. M. Bunten replaced 
the broken tube, which had been divided into inches, by a tube divided into centi- 
metres, and traced upon the slip of ivory a scale of 10 millimetres divided to every 0’2 
of a millimetre. I procured one of Ernst’s cistern barometers, which, after hanging 
all night by the side of the standard barometer of the observatory, was compared 
with it on the following day by one of the Assistants. M. Gambey was commissioned 
to construct a brass cylinder, either solid or, if hollow, air-tight, nearly of the dimen- 
sions of 91, a cylindrical cup to receive the kilogramme or the model, fitting into the 
cup of the stereometer, and a second cylinder closed at both ends, to fill up as 
much as possible of the space left vacant in the cup of the stereometer. While with 
M. Gambey, I ascertained that he had some platinum kilogrammes finished, with the 
exception of the final reduction. This appeared to be a favourable opportunity for 
commencing the formation of a collection of accurate copies of foreign standards, 
which had been recommended in Art. 33 of the Report of the Committee, dated 
December 21, 1841. Also the comparison of 91 with a copy having nearly the same 
density and expansion, and unalterable by mere exposure to the atmosphere, promised 
to be much more serviceable in finding the relation between the French and English 
standards of weight, than its comparison with a copy expanding nearly twice as 
much by heat, and having nearly three times its volume, and liable to become con- 
siderably heavier by oxidation in the course of a few years. I therefore applied to 
the Astronomer Royal for authority to purchase a platinum kilogramme for the use 
of the Committee. While waiting for his reply, I occupied myself with the compa- 
rison of 91 with PC No. 1-|-PC No. 2-1-B-l-V. 
The platinum kilogramme being a cylinder without a knob, does not admit of being 
lifted with a fork, consequently, in putting it into the scale-pan or taking it out, it 
must be held in the hand, a glove or a piece of silk being of course interposed between 
the fingers and the weight. The insertion of the hand into the balance case, and the 
communication of its warmth to the weight itself, are so prejudicial to the accuracy 
of a weighing, that it became necessary to seek for some method of obviating this 
source of error. Such a method was found in the employment of the detached scale- 
pans described in page 764, and answered so well, that I afterwards continued to use 
it in comparing weights of the usual form. 
On the 16th of September, the Astronomer Royal having approved of the pur- 
chase of a platinum kilogramme for the use of the Committee, I procured one from 
