US89585A - Improvement in stjn-dia - Google Patents

Description

,To all'whont it may concern:

itin/lied tat-*e5 JOHN JOHNSON, OF SACO, MAiNn.

. Letters .Patent No. 89,585, dated May 4, 1869.

IMPROVEMENT IN SllTN-IDHL'nS.l

The Schedule, referred to in these Letters Patent and making part of the same.

Be it` -known'that vI, J OHN JOHNSON, of Saco, in the county of York, `and State o f Maine, have invented a new and useful-Improvement in Sun-Dials; and I do, hereby declare that the following is a full and exact description of the same, reference being had to the accompanying drawings, making a part of this specication.

.My improvement relates to sun-dials of a globular form, the gnomon being dispensed with, and the construction very much simplified, the Whole dial, with out the stand, being in one piece.

It 'consists of a globe of ground glass, one side of which is rendered opaque by a coating of black paint.

This is the southern side, when placed in the proper position for use.

-The observer, standing on upon the ground glass, a small illuminated spot, the

position of which, both in a. horizontal and veiticaldirectiou, 'is variable with the change of the seasons,

Y and with the hours of the day.

This bright spot is caused by a pencil of the suns rays, which passes through an aperture in thel top of the hollow glass globe, the border of the hole heilig painted black, so as to cause a sharp definition of the spot on the northern side of the globe, and thus indicate the hour by illumination, instead of shadow.

In the drawing, the globe A is represented, supported by the-stand B.

'-The side toward the south is coated with black paint, C O, which excludes the sunlight, and partially obscures the interior of the globe.

At the top of the globe thereis a small aperture, D, through-which the raysof the sun enter, as shown at E, and fall upon the translucent ground glass at G.

the northern side, sees,

It is obvious that the bright spot, where the rays impinge upon the glass globe, will, in the morning, be seen on the right, and inthe afternoon 'on the left side,

while at noon it will be near the middle, and also at a lower point on the globe. n

In the course of-a year, the bright spot passes over the whole suifaceof the glass globe, occupying a different place every day, the position depending upon the inclination ofthe earths axis and its diurnal revolutiono At noon on the 21st of June, the spot is' atthe lowest point on the globe, markedy H, and, at the winter-solstice, it is at the highest point, marked J.

' It will be perceived, from this description, that this dial will give equated or'clock time without requiring any allowance or correction to be made for what is termed the difference between the sun and clock.

In this case, the hour-lines, marked 1, 2, 3, 4, &c.,

"will not be in the direction of true parallels of longitude, but will be-slightly curved to the' right or left, the extent of the curvature being the greatest when there is-the rnost difference between the sun and clock.

What claim, and desire to secure by Letters Patent, is-

A translucent hollow globe, having au aperture yat the top, through which a pencil of rays from the su'n may pass, to mark time, -the globe being rendered opaque at the top, and "on theside next to the sun, for the purpose of giving a perfect delineation of the bm'ghtspot, as it traverses the surface of\ the globe.

I vJOHN,JOHNSON: [L.s.] -Witnesses l Moses Eimer, F. W GUPTLLL.

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