An Explication o f the C u ts .
the following Obfèrvatïdns, which may not only be diverting to
the Curious, but likewife may teflcî tbtië^gobu of thé^F®I|ck
and perforation of the Mariners. It isObfervable, that finder the
line, the Mercury ftarée either flreP Or1 falls,? except about two
or three tenths, and will not ftir while they continue there, the
reafon is, either that the extraordinary heat there, fo rarities the
Air in the Tube, or that theEtherialParticles there^are fo clog’d
with the Rains of the Mofoons, thatthe Spring, of the Air is very
much weakened, and confequently ‘therefore cannot elevate or
deprefs the Mercury as ini other Ghmes. But when you come
into the Latitude of fiftèen degrees , either North or South, the
Mercury then will rife and fell an inch, when in thirty degrees
it rifes two inches,when iii forty five it rifèëthefi full threëiïïéhés,
when in fixty degrees Latitude^ it then fhortens and rëtüMa to
two inches, in feventy five it fhortens5 to an inch, ineightÿonè
it neither rifes nor falls a quarter of an inch. By an accurate Ob-
fervation of thefe, when rough tempefts, and imetpofin^GlOuds
prevent the taking of an Obfervation exa&ly^ the Marine«5 may
eafily fee in what Latitude he is in , and by that means may
perhaps by obferving his Compafs at the fame time, todèt him fee
whether he is North or South ; may not only frequently make
his Voyages in a much (hotter time} but likewifc prefefvi hil
Cargo. Which if throughly purfued, will notmnly be fel
traordinay ufe but Diverfion alfo. Thofe Baromètres Iveréin-
vented by the faid Mr.-Patrick^ who ii« both fdaffléw
them to the curious, and fupply afiy Perfon with them ; and' me-
thinks when both intereft and pleafure Prompt to a through Pro-
fecutionofthe Experiments,it cannot be reafonably thought that
a fuitable encouragement fhould be wanting. It is further remarkable,
that in thofe hot Climes, though the motion of the
Mercury is fo little, that in the variation of the Weather
it cannot but with great difficulties be obferved; yet by his Baromètre,
(hewing the motion of the Mercury upon the Declivity,
by having an account of the Latitude of the place, he adapts his
Baromètres to it, by which the different motions of the Mercury
are asdifcernibleas in different Latitudes.
This to be inferted after the Cuts of the Baromètres.