IMPROVED INSTRU- MENTS OR APPLIANCES TO BE USED IN SUBSTITUTION FOR GLOBES, WHETHER TERRESTRIAL OR CELESTIAL
Year: 1879

page_text: PROVISIONAL SPECIFICATION left by Denis Doyle at the Office of the
Commissioners of Patents on the 21st May 1879.
DENIS DOYLE, of Youghal, in the County of Cork, Ireland. "IMPROVED INSTRU-
MENTS OR APPLIANCES TO BE USED IN SUBSTITUTION FOR GLOBES, WHETHER
TERRESTRIAL OR CELESTIAL."
These improved instruments or appliances to be used as substitutes for terrestrial
globes consist, in the first place, of two, three, or four maps of the globe drawn on
transparent plates or discs made of glass, horn, mica, paper, or other suitable material.
Two maps, that is, one for each hemisphere; three maps, that is, one for each part
of the surface of the globe, comprising 120 degrees of its circumference; four maps,
that is, one for each quarter or 90 degrees of its circumference. Each map to be a
perfect delineation of the globe without perspective, or in other words, to be a
representation of the globe such as it would appear to an eye placed at so great
a distance from it that perspective would not be appreciable. However in such a
representation the parallels and meridians should be drawn for degrees, and if great
accuracy be required for smaller divisions, and a microscope used for their discern-
ment. Upon these maps also is to be drawn a figure corresponding to an
lemma on a globe, but this is to be drawn so as to show not only the sun's celestial
latitude or place in the ecliptic, but also the equation of time for any given day in
"
the year.
" ana-
Secondly, these improved instruments comprise plates or discs made of paper,
silvered brass, or other suitable material, upon which are drawn maps of the
meridians and parallels of latitude on the above principle of delineation. Also
around half its circumference, a graduated scale, showing the true altitude corre-
sponding to an apparent altitude for each degree of quadrant (or correction for
refraction), a line representing the wooden horizon, with compass points and degrees
for a zenith and amplitudes. Also a line 18 degrees below horizon for twilight,
and below that a slight shading to represent night. These discs to be laid under
and attached by a pin at the centre to the first mentioned transparent disc, so that
one may revolve freely on the other, and when great accuracy is required to have a
vernier and tangent screw. These instruments may be used as a quadrant if reflectors
were mounted. It may also be used by suspending a small plumb line from centre for
taking altitudes of sun or star, and thus may be found without calculation the time
of day or night (except time near noon) in any part of the globe by a pocket
instrument.

page_text: In like
The diameters of the first mentioned and the latter discs must be equal, and as
the space for degrees or minutes in both diminish towards the circumference, these
divisions must be marked and numbered as in a scale of natural sines.
manner a substitute for a celestial-globe may be constructed, and one lower disc
may answer for all by having the centre pin so as that the plates may be detached
at pleasure from one, and attached to another. Or instead of the two, three, or four
maps above-mentioned, one lower disc and a transparent disc, with a transparent
disc having on it a similar and equal map of meridians and parallels will answer,
provided a good chart is available, or a correct list of latitude and longitude of stars
and places. For solving problems for only one latitude, such as for London, one
plate will answer, the lines of the transparent plate elevated to the latitude being
drawn. By these appliances the problems on globes may be solved, such as to find
the rising and setting of the sun or star. The sun or star's amplitude and azimuth,
duration of twilight, time of day, the usual data as in globe books being given.
The rules for solving these problems closely resemble the rules in a globe book.
Problems in great circle sailing can be solved.
Within the circumference of the single plate for the latitude of London may be
read the rising and setting of the sun or star for any given day in the year. The
sun or star's amplitude or bearing at setting or rising. The sun or star's azimuth
The
or bearing in the heavens, or bearing of observer's shadow at any given hour.
sun or star's altitude at any given hour of the day or night. The length of the
longest or shortest days and nights. The duration of twilight, and those nights
which are all twilight. The proportion between the height of any spire building
and its shadow, etc., at any given time. These appliances will be found to work out
problems more accurately than ordinary school globes do. One plate moving hori-
zontally on another is not so liable to get out of centre from wear as a globe on its
axis, and the brass meridian on its bearings are, and even in new globes, the inner
edges of the brass meridian and wooden horizon are a short distance from the globe's
surface to admit of the free motion of the globe, when the quadrant of altitude is
between, and yet close contact (as in the appliances) is necessary for accurate
results.