The Madisonian. [volume] (Washington City [i.e. Washington, D.C.]) 1837-1845, 1844-03-08
Rev LIGHT,

NEW LIGHT,
Our attention has been called 10 the follow.
ing description, as given at a meeting OF the
American Philosophical Society Of new Lar
tern, which, we should think, might be advan-
tageously adopted by the Government in the
Light house establishment. The advantages
would be the great distance the light could be
seen by mariners, and the diminulion of ex
pense. What is vely remarkable, it will be
seen, is the fact that the light from small
lrick can be seen the farhesI.
From the .7r,ny and Many Chronicle.
REFLECTING LANTERN AND HELLO
TROPE.
Al meeting of the American Philosophical Socis-
ty, held in Philadelphia in March last, Major Ora
ham, Of the corps Of Typographical Engineers .
member Of The society, described Rejecting Lam
tern and Heliotrope, used by him meridian
marks for great dist ances in 1884, while tracing, in
his capacity Of United States Commissioners, the due
north line from the monument at the source Of the
river ST. Croix.
The lantern constructed by Messrs. Henry N.
Hooper Co, of Boston, under Major G.'s direc-
lions. II was similar in form to the Parabolic Re-
fecior Lantern someti es used in lighthouses, but
much 81 aer, to be portable.
The burner was Of the argand charac er, with a
cylindrical wick, whose Transverse section hall
an inch in diameter, supplied will oil in the ordinary
manner. This placed in the focus of a PARADE
lie r. hecor or parabolod, of sheet "copper" lined in
SIDE with silver about onewen'ielh Of an inch ia
h;ckness polished very smooth and bright. The d.
mansions were as follows
Diameter ofthe base of frusrum of reflector I6 ms
Distance Of vertex from base 375"
Distance Of focus from vertex 225"
Diameter Of cylindrical burner so"
Diameter of larger burner, which was
never used, but which, by adapting
piece, could be easily substituted l.25 /"
The instrument answered the purpose for which it
was intended admirably WELL and of great in
tracing the due north line While il occuped the
station Parks Hill fifteen feet above the surface Of
the ground, or 1928 feet above the sea- in the latter
part of September and early part of October, 1871
the light from il was distinctly with the naked
eye, al night when the weather clear from Bule
HILL, whose summit, where crossed by the meridian
line, is lO7 feet above the the intervening
try averaging about 500 feet above the sea, and the
| stations being sc miles apart.
The light appeared 10 the naked eye at tina. dis
lance, as bright and about of the same magnitude bs
the planet Venus. Viewed through the transit teles-
cope of 43 inches focal length, it presented Iumn-
| Gus disc of about 80 seconds Of arc in diameter
From its briiancy at that distance Major G.. has no
doubt that it would have been visb q to the naked
eye at 80 miles, and through the telescope at 100
miles, Couiu sta ons Tree from lnterpOsing Obects have
been found SO far apar.
II was remarked that The wick employed by Major
Graham was consider ably smaller than that usually
made, even for paror lamps; and to this he
trbuted, in great measure, the perfection with
which the parallel rays transmitted from the re-
fecing arabolc SUI face, to make them visible
at SO great distance. Though greater quantity of
light generated by larger wick the porlon of lays
reflected in dIeeon parallel to the axis, and which
alone come to the eye is smaller the flame tans-
cends the focal limit. The size Of the wick most ad
vantageous FOR use may easily be determined by ex-
pertinent. Major G.s impression is, that the smaller
It's transverse section, provided it is only large enough
to escape being choked up by the charred parc es,
even one-thrd or perhaps one fourth of inch the
farther the light would he visible.
Ii has occurred to Major G that lanterns of this
description might be used with great advantage as
station marks IN extensive trigonometIcal surveys
requiring primary triangles of great length of sides
revolving motion nigh, be gwen to the lanterns, so
as to make the light transmitted from them visible
| tine. Their simplicity, and the ease with which
they are managed would perhaps give them, for such
purposes, great advantage the Drummond or
Dude lights, even though they be not 30 brilliant as
| the latter.
The heliotrope which he employed in the day time
was made 10y order of Mr.. Hass err at the instrument
shop of the coast survey office. 1t was rectangular
paralelogram, of good German plate glass As by
10 inch IN size, giving of rejecting surface
| OF 10 100 square inches. his also was seen dis
timely with the naked eye at the distance of thirty six
miles.