THE NEW NATIONAL STANDAED OF LENGTH, AND ITS PEINCIPAL COPIES. 649 
“ That the thanks of the Committee are due to Mr, Sheepshanks for the spirit with 
which he has entered into the investigation of all the difficulties connected with the 
formation and perpetuation of a standard of length. 
“ That the Committee approve most fully of the steps taken by Mr. Sheepshanks in 
the preparation of new apparatus (as described by him), for the examination of all the 
causes of error, for the investigation of the thermometric correction, for the ascertaining 
the permanency of standard bars, and for the accurate comparison of bars. 
“ The question of adoption of the measures derived from the Survey was 
deferred.” 
Mr. Sheepshanks now turned his attention energetically to the practical preparation 
of the various apparatus to which his Report alludes. Of the details of the incessant 
labour of the next two years, few traces remain except in Mr. Sheepshanks’ correspond- 
ence with myself. But to these labours there was little interruption. Old apparatus 
was to be tested and new to be planned and carried into execution ; instrument-makers 
much occupied with other business were to be kept closely to the work ; manipulations 
of various kinds were to be learnt ; and all was done under the disadvantage of 
Mr. Sheepshanks’ domestic residence being at Reading, while the work of every kind was 
executed in London. The most tedious of the operations actually carried on appears to 
have been the preparation of original thermometers (or rather the acquisition of the 
experience necessary for their preparation, for I do not think that a thermometer was 
really finished before the end of 1847). It would seem that at this time there was no 
workman in London who could be trusted, without the closest superintendence even in 
the minutest points, to make a thermometer. At length Mr. Sheepshanks found him- 
self so far prepared that he deemed it necessary to apply to the Committee for further 
instructions. The following are extracts from the Minutes of the Meeting of 1847, 
.June 4 : — 
“ Mr. Sheepshanks made a statement to the following effect: — 
“ The tardiness in the proceedings connected with the Standard of Length has arisen 
from the delays incidental to the planning of new machinery, and of having it executed 
when all the workmen are busy, 
“ I conceive the ultimate object to be, to procure a permanent standard, which can 
be easily multiplied and widely distributed, which is to be connected with our best 
existing measures, with the base of the Trigonometrical Survey, and with the standard 
measures of other countries. 
“ But the immediate want is for an actual type of the standard measure. Therefore, 
although it will be desirable (in the scientific order) to end with establishing the 
standard, I believe it will be best for public convenience to begin with it. 
“ The first considerations which occupied my attention were the jpermanency of bars 
and the mode of perpetuating any measure. I propose to ascertain whether and how 
much a bar has altered in the following manner. Bars of different metals, of the same 
dimensions as those proposed for the standards, are to have each a yard marked on it, 
