Book-bot.com - read famous books online for free

The Discovery of the Source of the Nile by John Hanning Speke
page 44 of 672 (06%)

My first occupation was to map the country. This is done by
timing the rate of march with a watch, taking compass-bearings
along the road, or on any conspicuous marks--as, for instance,
hills off it --and by noting the watershed--in short, all
topographical objects. On arrival in camp every day came the
ascertaining, by boiling a thermometer, of the altitude of the
station above the sea-level; of the latitude of the station by
the meridian altitude of the star taken with a sextant; and of
the compass variation by azimuth. Occasionally there was the
fixing of certain crucial stations, at intervals of sixty miles
or so, by lunar observations, or distances of the moon either
from the sun or from certain given stars, for determining the
longitude, by which the original-timed course can be drawn out
with certainty on the map by proportion. Should a date be lost,
you can always discover it by taking a lunar distance and
comparing it with the Nautical Almanac, by noting the time when a
star passes the meridian if your watch is right, or by observing
the phases of the moon, or her rising or setting, as compared
with the Nautical Almanac. The rest of my work, besides
sketching and keeping a diary, which was the most troublesome of
all, consisted in making geological and zoological collections.
With Captain Grant rested the botanical collections and
thermometrical registers. He also boiled one of the
thermometers, kept the rain-gauge, and undertook the photography;
but after a time I sent the instruments back, considering this
work too severe for the climate, and he tried instead sketching
with watercolours-- the results of which form the chief part of
the illustrations in this book. The rest of our day went in
breakfasting after the march was over--a pipe, to prepare us for
DigitalOcean Referral Badge