, On the Figure of the Earth. 297 
to an elevation equal to the top of the instrument. In this in- 
strument the artist has avoided this inconvenience also; he has 
traced the point of coincidence on a little shell of nother! of- 
pearl; a lamp placed behind this shell illuminates it ; and acon- 
cave mirror, receiving the illuminated image from the point and 
from the plumb-line, reflects both at the bottom of the instrument, 
where the observer beholds them distinctly. In a word, that 
the observations may he made every where, the entire apparatus 
is fixed in a great portable tent, which shelters it, and the top of 
which admits the light by a kind of window, which opens for the 
observations. At Dunkirk this fine instrument, by the desire 
of the observers, was placed within the marine arsenal. The 
English brig the Investigator, which had conveyed it thither, was 
also to bring i it by the docks to the place where it was to be em- 
ployed, and was to remain there ready to take it back with the 
same facility, the same care, and the same respect as they would 
have paid to a vessel of our marine. We placed our little repeat- 
ing circle at a short distance off, ina shed which the Administra- 
tion of Marine had directed to be constructed for us; for it may 
be conceived, without our mentioning it, that the French govern- 
ment had given the necessary orders that the united observers 
should find all the assistance which they coulddesire. There, owing 
to a continuation of good weather, which proved extremely harass- 
ing, so little time did it leave us for relaxation, all the observations 
were completed in fifteen days, to which, properly speaking, we 
may add as many nights. By a confidence, which would not de- 
serve to be noticed if it were as common as it is proper aud use- 
ful, we reciprocally accommodated each other with our appara- 
tus; and when we were completely satisfied with our observa- 
tions, we made a full and entire communication of them to each 
other. They were found to agree in a surprising manner, if the 
different nature of the processes be considered ; and what is still 
more fortunate, they were found also to adcord perfectly with 
those which M. Delambre had fornierly made in the same place, 
in the commencement of his operations ; whence results the 
double assurance, that the arcs of France and England are thus 
perfectly connected with each cther; and that, moreover, the 
observations made on the other points of the two ares, by pro- 
cesses similar to those which we had proved together, afford all 
the precision which can be desired. It gives one un‘eigned sa- 
tisfaction to recognise as certain, results that have cost so much 
trouble. It isa great encouragement for science, to see that it can 
at length calculate on the methods which it practises. Though 
instability, i in this particular, is infinitely less dangerous than in 
politics, it is still an evil, because it is an acknowledgement of 
imperfection. Happily, the learned ought to take less pleasure 
in 
