two hemifpheres. But however plaufible this theory may
fcem, at firft fight, experience has abundantly detected its
fallacy.
cin'thefe feas, the variation of the needle at Cape Circumcifion muff'have been 10“
Wefterly: whereas, in the moft Wefterly point o f Captain Cook’s trait, where he
was fufficiently near the parallel o f 54.° South, to have feen land fituated in it, the
variation was 13° j Wefterly. This difference o f 3°'f, in the variation, anfwers to
about 7° of longitude, in this part of the-parallel of 54° South : and by fo much did
Captain Cook fall in with this parallel to the Eaftward of what he Ought to have done
to fee the land in queftidn. « Hence (M. Le Mènier fnfèrs), that it is not furpriz-
“ ing the Britifli navigator Ihould not find Cape Circumcifion under a meridian
“ which is 28° \ to the Eaftward. of Ferro, when it is really fituated under a meridian
“ which is but 210 § to the Eaftward o f it.”
In replying to thefe allegations, I filali, firft, (hew, that, granting the dependence
which M . Le Monier fuppofes may be placed on obfervations o f the variation
made at fea, hehas ftated the quantity o f the variation, obferved on hoaral the Refolu-
tion, very erroneoufly.
Secondly, I fhall prove, beyond contradiction, that obfervations o f the variation,
made at fea, cannot be depended on, for the purpofes to which M . Le Monier has applied
them. . ’ v
And, daftly, that no material error had crept into M . Bouvet's reckoning ; but that,
i f any error did exift, at muft have been o f a contrary nature to that which M , Le Mo-
nier fuppofes. , .
That M . Le Monier lias not given altogether a true reprefentation of the matter
will appear from hence. On the .16th o f February, atnoon*, the Refolution was in
-latitude 54° 3.1 South, which is fufficiently near the parallel of 54° South, to fee
highland, the. Northern extremity o f which lies to the Southward of that parallel-
and-at that time we were in 6° Eaft o f Greenwich, or 23° ! Eaft of the .¡Hand of
■ Ferro. : that is, 4” lefs than is affigned for our fituation by M . Le Monier On the
■ evening .of the fame day, the fhip being in latitude 54» 24', and longitude 6” 30', on
24V i Eaft o f Ferro, the variation was no more than 12° 7 Weft, which alfo is near a
degree and half left than M . Le Monier fays it was, when we firft arrived in a proper
.parallel for feeing Cape, Circumcifion. It is true, thè next morning, in latitude
•54 2 I Ì South, longitude 8° 6 'Eaft, we had 13” 42' Weft variation ; but this was
after we had run more than two degrees within fight of the parallel of 54» South! It
is, moreover, highly probable, that both, thefe variations were too great ; for, on the
27th, in the evening, latitude.54° 25' South, and longitude 9“ 20' Eaft ; that is, 1° J • '
more
, * L 1“ ! ' b5,, tb' '’jjSS i" “ The Original Allronomical Obfervations,” printed by or-
U g g ì * *'WCh’ ^ ^ » “ ““ X «7W. ¡ £ »
fallacy. In confequence o f Captain Cook’s voyage, now
under confideratidn, We have a thorough knowledge of thé
ftate
more to ihe Eaftward, and after we 6ad run 3® 4 Oft the parallel we wére then on, the
variatiôn was no more than 130 16' Weft. It is alfo worthy o f remark, that on the
14th, in the evening, latitude 56° I4x" South; and longitude 40 5o' Eàft, which is
but i° 1 o ' to. the Weftward of the point, where the Rafolution came firft into it
proper fituation to fee land, fituated in the parallel o f 54° South, the variation obferved
was no more than 6° $o' 'Weft. And we may further, add, that on the ift of March,
1774, the Adventure had no more than 12° i Weft variation, though ihe was then -
confiderably both to the Northward and Eaftward o f our fituation on the 17 th of Fe_
bruafy in the morning, onboth which accounts the variation ought to have been
greater, inftead o f a whole degree lefs. Frota all thefe circiimftances, there can belittle
doubt but that the two variations, obferved by us on the 16th and 17th of F e bruary,
were too great or that the variation, at the point where the Refolùtfon firft
came fufficiently near the parallel of 54° South, to fee land, the Northern extremity
o f which is fituated in that parallel, could not be more than n ° f Weft, ihftead o f
1 3° i » as jSjpi Le Monier has reprefented it.
Under this head of enquiry I may alfo obferve, that although the Refolution was too
much to the Southward o f the parallel o f 54° South, when ihe croiTed the meridian *
which is 21°\ to the Eaftward of Ferro ; that is, 3° | Eaft of Greenwich, the Iongi-.
tude which M . Le Monier affigns for Cape Circumcifion, .to fee if it had been in that
fituation ; yet her confort, the Adventure, was for feveral degrees on éach fide o f that :
meridian j and efpecially when ihe had io ° | of Weft variation, full as near-to the parallel
of 54° South, as M . Bouvet was to the land when he faw it * : and on the day
that ihe a&ually pafled that meridian, had fine dear weather f . Hence, therefore,
grânti^ M. Le Monier his own arguments, which, however, I have proved to be
erroneous; and that obfervations made at fea, for the variation o f the compafs, maybe
depended on for the purpofe.of finding the longitude, it is ùtiérly impoffible that
both the Refolution and Adventure could have pafled Cape. Circumcifion without
feeing it. But I ihall now flievv,. that thefe obfervations are liable to a much greater
error than the whole quantity, fo vigoroufly infilled on by this gentleman.
I will not here run the riik of incurring M. Le Moniêr's difpleaiure, by calling the
accuracy of M . Bouvet's obfervations in question ;..but will admit every.thing that he
himfélf can think due to the inftruments and obfervations o f that deferring -navigator.
It is enough for my argument, and it is but too evident; from the obfervations them- -
felves, that ours were by no means capable of determining the variation to fo fmall a
quantity -,
ty*Mn'DTafty°pfe!np. 0bftrVatiOTS’ P- and FduVetVVoyage,. publirtird.
t See the Obfervations, p. 21.8a.