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JOURNEY OF MAUPERTUIS. 249
was not more than half a degree ; confequently there was no room for apprehending
that our telelcope in a pofition fo nearly vertical fhould have fwerved in the {mallelt
degree.
Although for all thefe reafons.we could not doubt of our amplitude being correct,
we were defirous of proving it fo by experiment : and for this purpofe we employed a
proof of the moft laborious defcription, but beft calculated to fatisfy us as it would fhew
us at the fame time the exactnefs of our inftrument, and the precifion which we might
reckon upon in the arc we had taken.
‘This proof confifted in afcertaining anew the amplitude of the fame’ arc by another
ftar. We waited then for an opportunity to make fucceeding obfervations of a ftar,
which in this country is difficult, fince it feldom happens that three or four finé nights
follow each other: and beginning on the fevénteenth March 1727, to obferve the ftar a of
the dragon from the fame {pot as before at Torneo, after taking three nice obférvations
of the fame ftar, we departed to take correfponding ones at Kittis. On this occafion
our fextant was conveyed on fledges at a foot pace over the fnow, the moft eafy mode
of conveyance that can be imagined. Our fecond ftar pafled even nearer to the zenith
than the firft, fince it was no more than a quarter of a degree from the zenith of Torneo.
‘Yhe meridian already traced in our obfervatory at Kittis enabled us to fix our fextant
in very little time, and on the fourth of April we then began our obfervations on a.
We took three obfervations at Kittis as well, which, comparing with thofe of Torneo,
gave for our amplitude 57’ 303” which made no greater difference between this and
our obfervation on 8 than 34”, after making allowance for the obfervation of light.
And not admitting the theory of the abberration of light, the amplitude by the laft
obferved ftar did not differ a fecond from that found by the firft.
The argument of the two amplitudes with fo very flight a difference, a difference which
will even be fhewn to be lefs than it now appears ; this agreement afforded the moft folid
proof of the exactnefs of our inftrument, and of the perfect precifion of our obfervations.
Having thus repeated our work, we found that by a mean of the two amplitudes, the
amplitude of the arc of the meridian between Torneo and Kittis, was, 57’ 283” which
compared with the length of that arc 55,0234 toifes, gives for the degree which cuts
the polar circle 57,437 toifes, a greater length by 377 toifes than that which was
afcertained by M. Picard between Paris and Amiens, which he made to be 57,060
toifes. It is however neceflary to remark that, as the aberration of the {tars was not
known in the time of M. Picard, he could make no allowance for it: if this be done
for him, and the additional ones for the preceffion of the equinox, and. for refraction,
which M. Picard omitted, be added thereto, the amplitude of his arc being 1° 23/ 63”,
and the length 78,850 toifes, it will give for the degree 56,925 toifes, and make it lefs
than ours by 512 toifes.
And were aberration not admitted, the amplitude of our arc would be 57’ 25’, which,
compared with its length, would make the degree 57,497 toifes ; longer than the de-
gree meafured by M. Picard by 437 toifes.
To conclude, our degree, allowing for aberration, varied g 50 toifes from what it fhould
have been according to the computation of M, Caflini in his book of the Size and
Figure of the Earth; and differs 1000 from it, if aberration be not allowed.
From which it is apparent that the earth is confiderably flat towards the poles,
During our ftay in the frozen zone, the froft remained yet fo fevere, that on the
feventh of April at five o’clock in the morning the thermometer funk to 20° below the
freezing point, although every day at noon it rofe to from 2% to 3° above it, thus
changing as much between morning and evening as it does in common between the
VOL. I. KK greateft
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