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V. On the length of the French Metre estimated in parts of the 
English standard. By Captain Henry Kater, F. R. S. 
Read February 5, 1818. 
One of the objects of the committee of the Royal Society 
appointed for the purpose of determining the length of the 
seconds pendulum, being the comparison of the French metre 
with the British standard measure, two metres were procured 
from Paris for that purpose, the one made in the usual man- 
ner and called the metre d bouts , and the other a bar of platina 
on which the length of the metre is shown by two very fine 
lines ; this is named the metre a traits. 
The width of the metre d bouts is one inch, and its thickness 
0,3 of an inch. On one side the word “ Metre ” is engraved, 
and on the other “ Fortin a Paris/' The terminating 
planes are supposed to be perfectly parallel, and the distance 
between them is the length of the metre. 
The metre d traits is the same width as the metre d bouts, 
but only a quarter of an inch thick. The lines expressing 
the length of the metre are so fine that one of them is 
scarcely perceptible even with the assistance of a microscope, 
unless the light be very favourable. The situation of the 
lines may however be discovered by two strong black dots 
made with a graver at the extremities of each, and a fine line 
crosses them at right angles to indicate the parts from which 
the measurements are to be taken. 
This metre previous to being brought from Paris, was 
