Full resolution (JPEG) - On this page / på denna sida - Pages ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
PHIPPS’S JOURNAL. 593
*¢ There were two time-keepers fent, out for trial by the Board of Longitude: one
made by Mr. Kendal, after Mr. Harrifon’s principles; the other, by Mr. Arnold : this
laft was fufpended in gimmals, but Mr. Kendal’s was laid between two cufhions, which
quite filled up the box. They were both kept in boxes {crewed down to the fhelves of
the cabin, and had each three locks; the key of one of which was kept by the captain,
of another by the firft lieutenant, and of the third by.myfelf; they were wound up each
day fuon after noon, and compared with each other and with Captain Phipps’s watch.
They {topped twice in the voyage, owing to their beirg run down; they were fet
a-going again, and as they had been daily compared together, it was ealy to know how
long each had ftopped, from the others that were {till going ; this time is allowed for in
the table of the mean time at Greenwich by each time-keeper.
“ When we were on fhore at the ifland where we obferved July fifteenth, we
found how much the watch was too flow for mean time. When we returned from the
ice to Smeerenberg, and again compared the watch with the mean time, allowing the
{mall difference of longitude between the ifland and Smeerenberg, we found that it went
very nearly at the fame rate as it did when tried at Greenwich: fo that its rate of going
was nearly the fame in our run from England to the ifland, from thence to the ice and
back again to Smeerenberg, and in our voyage from thence to England, as we found on
our return. By this means we were induced to give the preference to the watch, and to
conclude that the longitude found by it was not very different from the truth.
“< The principles on which this watch is con{tructed, as I am informed by the maker,
Mr. Arnold, are thefe: the balance is unconnected with the wheel-work, except at the
time it receives the impulfe to make it continue its motion, which is only while it vi-
brates 10° out of 380°, which is the whole vibration ; and during this {mall interval it
has little or no frition, but what is on the pivots, which work in ruby holes on dia-
monds: it has but one pallet, which is a plane furface formed out of a ruby, and has ne
oil on it. \
‘© Watches of this conftruction go whilft they are wound up; they keep the fame
rate of going in every pofition, and are not affected by the different forces of the {pring :
the compenfation for heat and cold is abfolutely adjuftable.
‘“* Time-keepers of this fize are more convenient than larger, on feveral accounts ;
they are equally portable with a pocket watch, and by being kept nearly in the fame de-
ree of heat, fuffer very little or no change from the viciflitudes of the weather.
‘* This watch was exceedingly ufeful to us in our obfervations on land, as the other
time-keepers could not fafely be moved : and indeed, in the prefent voyage, where they
were on trial, it was contrary to the intent for which they were put on board, and might
have been attended with accidents by which the rate of their going might have been
greatly affected. .
‘“* The longitudes by Mr. Arnold’s larger time-keeper are very different from thofe
by the watch in our voyage back from Spitibergen to England; owing, probably, to the
balance-fpring being rufted, as we found when it was opened at the royal obfervatory
at Greenwich, on our return.
** The longitudes found by the moon are deduced from diftances of the moon from
the fun’s limbs, or from ftars, taken with the fextant ; whilft the altitudes of the moon
and fun, or ftar, were taken by two other obfervers.
*< Tn one inftance (June the twenty-fixth) the obfervations were all made by Captain
Phipps with the fmall fextant fucceflively ; and the altitudes of the moon and {un at the
very inftant the diftances were obferved, are deduced from the changes in thefe altitudes
during the interval of obfervation.
VOL. Ie 4G « I have
<< prev. page << föreg. sida << >> nästa sida >> next page >>
