US106718A - Improvement in solar-time instrument - Google Patents

Description

'2 sheets-sheet 1.'

P. M. PANNBTRAT.

= lI'ime Instrument.

V` Patented Aug. 23, 1870.

No. 106.718:v

Figi' A Winesaes I l 'i lnVenor- 2 Sheets-Sheet 2.

1P. M. PANNBTRAT.

. Time Instrument.

No. 106,718. Patented Aug. 2a, 1870.

" FigA/l.

FlgXU diritta tatca Latent (fettine.

Letters Patent No. 106,718, dated August 23, 187 (t.

IMPROVEMENT IN SOLAR-TIME IN STRUMEN T.

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

To all to lwhom t' t may concern Be it known that -I, Fnalvcors MARTIN PANNE- TRAT, of Paris, in the Empire ot' France, have invented a new and improved Astronomical Instrument called the Heliade, by means of which is obtained the true time at mid-day, or at any other moment of the day, the latitude, the longittide, and the meridianline; and I do hereby declare that the following is Va full and exact description thereof, reference being had to thc accompanying drawing and tothe letters ot reference marked thereon.

In these drawing- Figures'l, Il, III serve to demonstrate the principle ou which this instrument is based.

`Figure IV is a front view, and

Figure V, a side view of the said instrument, with a series of alidades and dials on one side, and on the other a metal disk, B, to counterbalaucethe weight of the alidadcs and dials.

Figure. VI is the developed plan of the interior Vof' the box making part of this instrument.

Figure-VII is a graphical view otthe said interior undeveloped.

Figure VIII is an oblique view of the instrument` with a series of alidades and dials on each side of the box.

Figure IX is a side view ot' an instrument, with a single demi-cylinder. ltigureXis a small pocket instrument, its case servmg as its support. v

Figures XI and XII are, the former a plan ot' a balance doubled and multiplied; the latter a vertical vsection of the leg ot' the same, for maintaining the equilibrium of the instrument.

This invention relates to an instrument intended to measure, with the help ofthe sun, in all places in the world, on land or on sea, lirst, the true time of midday, or, in other words, the moment ofthe passage of the sun over the meridian; second, the latitude at all times of the day, as long as the sun is above the hori-v zon, thc true time heilig known; third, the true time of the place where one may be at every instant of the day, the latitude being known, approximatively; fourth, the longitude ot' the place where one may be; lit'th, the meridian-line, or true north and south line, and, consequent-ly, the declination of the compass, or the varia-tion. t

It' this instrument does not leadv to the complete suppression of the sextant and other reflecting-instruments, of the chronometer, and of the compass, at least it will be found indispensable for controlling and regulating with nicety these diti'erent instruments-and the operations elected with them. It dispenses almostentirely with all calculations,-and reduces the `observations to a greatsimplicity, and, at the same time, insures an exactitude almost mechanical. I t does not, consequently, demand any deep theoretical study. It is independent of atnmsphericinfluence. Finally, it has the advantage of being capable, if necessary, ot' replacing, alone, all the other instruments, viz., sextant, chronometer, and compass.` v

The size of this instrument is variable. It maybe reduced to the size of a large snuff-box, and thus carried in.the pocket; or, if great exactitude and precisiou are required, this size may be proportionately increased.

It is important, before entering into the explanation, to give an idea of the problem to be solved. This will, be done by referring to Fig. I of the accompanying-drawing, which also sets forth the relations bctween the instrument andthe terrestrial globe. Suppose D the place whose position is to be determined on the sphere represented by the circumference E g' E' g, and whose axis from one pole to the other is shown bythe line g g', and the line E E indicates the equatorial plan, it is required to find whatdistance separates the point D from thc point E, or, iu other words, from the equatorial line, that which is eliectcd by astronomically measuring thel distance from the point Z, zenith of the observer, to the point Z, equatorial zenit-h, by drawing from the points Z and Z the lines Z E E and Z D D', which meet at the point I), the center of the sphere; we have thetwo angles E I D and D P E', equal to one another, as also the arcs E D and D' E', both similar' to the arc Z 7'. Consequently, it' a method of any description enables one tomea-sure the arc DVE', the measure of the arc Z Z will be obtained, also, and, therefore, that ot' the arc E D. It is precisely this that thisinstrument is intended to efi'ect.

This instrument consists ot' a rectmigular box, A, lung` so as to turn on two pins, b b', and whose axis passes through the center ot' the volume of the box in the direction of its length.

The axis of the two standards c c is perpendicularto the base D D', which pivots horizontally, at T, on a support, whose legs, d d d, are composed of screws, by means ot' which the basemay be maintained in a perfectly horizontal position, which forms an essential condition for the exactitude ot' the observations.

This true horizontal position is ascertained by means of two water-levels, n n', fixed, at right angles,

on the base.

A screw-nut, s, serves to arrest the pivoting movement when the. box is in the desired position.

Inside the box are two hollow demi-cylinders, with their convex parts standing back to back at the center of the volume of the box, (see Fig. VII.) Their bases form exact half circles.

These cylindcrsane graduated in their conca-ve part by means of lines parallel with the heini'cyele of the base, and of others,perpendicular to the first, and par all'el -with the generating-line of the cylinder. Fig. VI represents these graduations developed in a plan Thus arranged, these two demi-cylinders represent exactly, each of' them, the section of a part of one of the hemispheres included between the two tropics, (see Fig. II,) graduated in its concave, instead ot` in its convex part.

The line E E', (Figs. II, VI, and VIL) which divides the longitudinal lines into equal parts, represents thc equator; the others, above. and beneath, marked 0 to 24, representthe degrees of boreal and austral declination of lthe sun from one tropic to the other. The distance intervening between said lines increases gradually from the first (the nearest to E E', which is marked zero) to the last, according to the principle demonstrated, Fig. III. Thus, by taking the line g g as the axis of the earth,-the point l as the center of the sphere, the arc g 0 g as a meridian, the p oint 0 as one of the points of the equatorial line, the points a b c as degrees of iutertropical latitude, and then if from the center P two radii are drawn, which, after cutting the circumference at thepoints a l) c, extend far enough to moet the tangent M M', it is clear that the divisions 8,' 16, and 24 increase in proportion as they depart from 0, in a progression of which it is important to take account, for the greater precision of the observations.

The other lines, perpendicular to 'the former, and equidistant fi-oin one another, are the meridians. The middle one, M M', marked 12, (see Fig. VI,) being thegenemfting-liue of' the cylinder, represents the midday of the place, and the other to the right and tothe left, marked l to 6, and 6 toll, the horary lilies of the diurnal arc, with subdivisions, by fractions, of 2O. 30', say ten minutes of time.

A thread, g g, Fig. VII, perpendicular to the long sides of the box, and corresponding exactly to the'line M M', serves as axis to each ofthe dcu'ii-cylinders.

At the center of this thread is a knot,P, which should correspond with the point() or G9 of the line M M.

In order to obtain this precision, the thread is re.- taiued in g" g by screws, which enable one to bring back the knot to the center, which is determined by placing a second thread in the length ofthe box from E to E', the extreme points of the equatorial line. The place where this second thread will cut the first will be the precise cerner sought for. The thread g" thus represents the axis ofthe earth, ot' which the knot is the true center, (see Figs. 1I and lll.)

On a board, N, attached, by hinges, to one of the large sides of the box, so as to remain applied, or to be withdrawn, at will, exists a compass-card, whose north and south line is precisely in the plane of thc g thread g" g", and of the line M M'.

This board maybe equally well placed ou either side of the box, provided that, whatever be the slope of this latter, the said board be held. horizontally. lt could also be so arranged as to act., at the same time, as cover or lid to the box.

The upper demi-cylinder serves for the observations from 6 a. 1n. to 6 p. ni., the lower one before 6 a. in., and alter 6 p. m., in high latitudes, or when the sun is continually at the edge of the horizon, that is to say, in the polar regions. And, as this latter is very rarely used, it could, with a View of simplification and economy, be suppressed, as shown in Fig. 1X.

At the foot of one of the vertical standards is fitted a quarter circle, 13, graduated fi'oni 0 to 90.

An alidade, Gr,l is fixed to rest at the axis l: of' the box, which axis is the center of the circle ot' which the dial B is an are, so that, by running the alidade on the dial, a rotating motion is imparted to the box, whichslopes, and describes, on the plan E P E O, (see Figs. II and VIL) an arc exactly similar to that described by the alidade on the dial.

This dial'could rigorously suffice if the alidade were furnished, like those of'sextants, with a vernier or nonius giving the minutes and the seconds, and, according to the size of the instruments and the degree of precision required, the observation may be arrested here. Nevertheless, toat-tain a higher degree of exactitude, it will bc better to apply the following improvement to the instrument:

At the top of thealidade G a second dial, g, will be seen. A secondalidade,--H, is attached by a pin onto the first', at* the point p, which is the center ofthe circle of which the dial g is an arc; this latter alidade plays iu thc-contrary direction to the first, G. At the head-of this second one, that is to say, on the prolongation of the radius under the center,1), and forming wit-h it a'broken line, exists a little hand, which exactly covers the indicating stroke of the alidade G. The indicator of the alidade H is then, at the extreme left of the dial g, destined to give the fractions of degrees in minutes. To divide this dial, the alidade H is first placed in this position, and in front of the indicating stroke on the alidade, ou the dial g, is traced a line which is the prolongation of said stroke, and marked O. The indicator G being 4then placed in front of any degree-line but zero on the dial B, the alidade H is run out until its head hand, changing from right to left, has measured, backward ou the dialB, the space of a degree, that is to say, until its point is found exactly in front of' the division which precedes that marked by the indicator G. The indicator H has then passed to the extreme right of the dial g, on which is traced a stroke marked 60, which is the prolongation of the stroke of the indicator of the alidade, and the are intercepted by the two points 0 and 6U, similar to the arc described by the hand, is divided into sixt-y sections, equivalent to as many minutes.

In order to obtain the complement of fractions a third dial and alidade are required. This third dial, h, is on the pin ofthe alidade H, upon which the third alidade, L, is fixed by a piu at'vn. This latter is the radius of the circumference, ot:` which the dial h is an arc. lts head has a hand which fulfills, inrelation to the divisions of the dial y, the saine functions as the one placed at the head ofthe alidade H in relation to the divisions of the dial B. To the extreme left-of the dial h the line O is tr'aced, being a prolongation of the stroke of the indicator L, and the same proceeding is effected as before, dividing in to sixty parts, which will represent seconds, the space run over by this indicator ou thc dial h, while its hand will have measured-backward one of thedivisions of the dial y. By this means, it' it is judged necessary, fractions of one-third may he talien into account; for this purpose a fourth alidade, M, being pinned to the end ot' the alidade L, indicator of seconds, whose indicating stroke, at its point, is run on ay fourth dial, placed ou the piu of the alidade L, which dial has been divided into sixty parts, which are thirds of seconds, iu the. same way as the others, by means of the hand at thel head of the alidade M.

It will be understood that a number of combinations could be included in the construction of an instrument on this principle, each of whilch would be prefer'- able according to the requirement-s ofthe accompanying circumstances, that is to say,accordiug to the importance, more orless considerable, of the questions of weight, volume, and delicate nat-ure of such an instrument.

Fig. VIII represents the same, with a double play of alidades and dials, one on each side of the box-f an improvement which not only affords greater convenience, but is alsean extra guarantee for evennessand for precise solutions.

In Fig. IX, which represents, as above described, an instrument with but one demi-cylinder, viz., the upper one, the axis of suspension and rotation 0l' the box, instead of passing through the cent-er of the volume, is lowered, so as to pass continually through the point O, (see Figs. 1I, III, and VII,) which, in this case, lies directly on the bottom, being intended specially to realize a'reduction in the general proportions ofthe instrument, principally in theheight, and thus necessitates certain modifications in the measuring apparatus. Consequently a single dial, g, is fixed, not'to the foot of one of the standards, but to the right-hand corner of one of thesmall sides of the box itself, so that the first stroke of this dial to the left,

- marked zero, is entirely included in the supposed plan,

E P E O, Figs. II and VII. A single alidade, G, which is iirmly connected to, and extends in a vertical direction from, the corresponding standard on the 'axis of the pin d, serves to mark the divisions of the dial, which are only degrees. To trace these divisions the box is caused to turn in such a way that the sides b a b' change the vertical position they occupy for a perfectly horizontal one. This results iu the supposed plan E P E 0, also changing from vertical to horizontal, after having run over an arc of ninety degrees, which the indicator ofthe alidade will have duly registered on the dial. In coincidence with this indicator another line is then traced to the right of the dial, which is marked 90, and the space included between these two extreme lilies is divided int-o ninety fractions, each representing one degree.

Fig. X is a smallpocket instrument, its case serving as its support.

VTo effect an operation, that is to say, an observation, all the indicators should he brought onto the zeros, connnencing wit-h the indicator of' the thirds, if the instrument has one; otherwise by the one denoting seconds, then the minutes, and finally the degree. For this purpose the box should be perfectly perpendicular; in other words, thc supposed plane which passes in E O Il P, Fig. II and Fig. VII, ought to he quite vertical. 'Ihe line Z I) l 1)', Fig. I, that is to say, the' terrestrial ray, in its prolongation as far as the zenith ofthe observer, passes infallibly tlnough the points O I of the Figs. II, III, and VII, inasmuch as the graduated demi-cylinder represents the lower hemisphere g E' g', Fig. I, of the planet. This condition of verticalness is simply a question of level.

Io find the exact time of mid-day with this instrument, (this problem being in relation and essential for the solution of all others,) and without the -aid of any other, the observations should commence at the moment' that the sun is approximately judged to be on the point of reaching its greatest height, that is to say, of 'passing over the meridian. lhe operation is then pursued as follows:

The base being perpendicular, and the indicators ou the zeros, t-he instrument is so placed that the box, in turning on the axis b b', slopes toward the sun, that is to say, toward the south, if the observer is in the boreal hemisphere, and toward the north if in the austral hemisphere.

IVe shall` only speak of the observations made in the boreal hemisphere, and of those with the upper demi-cylinder, as all the other observations are identical.

rIhe instrument is then set by turning the hase horizontally from right to left, or from left to right, on the point T, until the shadow of the thread y" g' exactly covers the line of the meridian M M, Figs. VI and VII; then, still maintainingit thus, the box is turned vertically, by pushing the alidade G on the dia-l B, until the shadow of the knotreaches the intersect-ion latitude ot' the place will be 460. had been 190 44' the shadow' of the knot would have of the line M M', and of the longitudinal line, which represents the declination ot' the sun calculated for the day, (for this, a knowledgeot` the time-tables, or,

at least, of cphemeris gvingthe equation of time and the declination of the sun, is requisite.) Itis evident that if the declination is boreal, the observer being in the boreal hemisphere, thc shadow of the knot will fall'- below thel line E E', it',` on the other hand, the declination is austral, it will fall above the same.

Suppose the first hypothesis. The shadow of the knot is thus below the line E E', as long` as the sun rises this shadow will'incline to descend, which will necessitate the prolongation of the vertical movement of the box, so as to maintain this shadow en the desired line. A fugitive but appreciable moment will at last arrive when this `shadow willhecome statiout ary before inclining to reascend; it is this'passing but appreciable moment that must be arrest-ed to rapidly ix the box by the screw of the alidade vGf which will be the precise time of mid-day, in other words, the precise instant the sun passes over the meridian and inclines to redescend.

Observation being then taken ot' the figure of the divisions marked by the alidade G on the dial B, the?"- exact latitude ot' the place is obtained; this alidade, which, as previously mentioned, pivots on the same axis, and, at the same time as the box, having described on this dial an are-similar to that described by the box in its revolution toward the sun. Under this new condition the line EI E Z, Fig. I, that is to say, the terrestrial radius, ,in its prolongation to the equatorial zenith, passes through the points 0 1, Fig. II, III, and VII, instead of the line D' P D Z', and the arc Z Z is measured.

It is now that the lines of declination prescut'their great importance. If the terrestrial axis were unchangeably perpendicular to the plane of the ecliptic the sun would be continually at Z at mid-day with regard to the observer D; but it is not so, and, for example, it' it be supposed at any other point S of the intertropical zone, Fig. I, it is evident that by inclining the box representing the lower hemisphere g E' g', so that the shadow ot' the knot may fall on the central point 69, the arc Z' S will alone have been real y measured, and, to the measure found, it will be necessary to add the known measure of the arc S Z. (If the sun was in the other hemisphere it would have to be deducted.) Ihis work is avoided by this instrument, which, itself, takes account of the declination. Nevertheless, a small calculation of this nature will become necessary whenever the calculated declination presents' fractions. As, in consequence ofthe:v size of the instrument, the divisions representing the degrees ot' declination are always too near to one an' other to admit of subdivisions, the fractions .must at first' be neglected, that is to say, the shadow ofthe knot must be made to coincide with the line to which it isl nearest, which will of necessity give a few minutesand seconds more or less. Suppose, for example, the declination of the day to be 190 1li', the shadow ot the lmet must be made to coincide withtheline 19, save to add the 16 to the figure, read on the dial at'- ter the operaton. Let this gure`be-45O 44', the If the declination been made to coincide with the line 20, and 16 would have to be deducted from 45o 44 which leaves 45 28'.

If the indicator does not correspond exactly to a degree line on the dial B, but gives a fraction, for example, 480 and a fraction, in order to know what this traction represents in minutes and seconds, the following operationnmust be observed:

rIhe alidade H must be moved, so as to bring the hand on its head round onto the line 48 of the dial B, andthe space run over 'in the contrary direction by the indicator on thc dial g will determine the number of minutes. rlhis number may itself have a fraction, suppose this number to be- 3-L-I-X. To determine this fraction the same proceeding must be executed with the alidade L, thehand on the head being brought round onto the line 34 of the dial g its indicator will theu niark the complement of seconds on the dial 7i.; suppose these seconds to be 25, the latitude found will be at halt' a second, nearer 480 34' 25".

To find the latitude at any other time ot' the day not mid-day, the true time must beknown, being obtained by the ordinary observations and instruments.

The box is placed in such a position that the sliado\v-ot the thread covers the horary line corresponding to the known time, and it is inclined at the same time until the shadow of the knot falls on the line ofthe declination, as calculated. The arc run over by the indicator to arrive at these coincidences measures, necessarily, the latitude ot' the place.

'lo find the true time at any other moment of the day than at mid-day it, is requisite to kiiow, at least approximately, the latitude of the place where the observation is to be made. The morningr and the evening a slight difference in latitude is ct' little. importance. The indicators are arranged so as to niark the latitude, say, for example, 480 To begin, the indicator of seconds is placed on 25 ot' the dial h. -It is then obseived that the needle at its head has measured in the contrary direction, backward from the lzero of the dial g, a fraction necessarily equivalent to these 25"; consequently, the alidade H has only to be rmi out until this hand be on the'division 34 of the dial g, for the indicator H to measure thereon forward the 25". In this movement the alidades hand measures downward, backward from the zero ot' the dial B, the fraction equivalent to 34 35", and the alidadc G has only to be pushed.4 until this hand arrives at 48 for the indicator to be iii advance between 48 and 49 in the exact proportion ot these 34 25". 'lhe box will thus have the inclination necessary to measure the h orary angle. The base is *K then made to pivot horizontally, so that the shadow ofthe knot falls on the line ot' declination of the day, and remains on this line. During this ktime tbc shadow'of the thread is projected parallel with the horary lines to tipe right aiul Iel't ot' the 4line M M', Figs. VI and V I, according to whether it is before or after noon, and it passes, necessarily, from one to the other every ten minutes. As soon as it covers one of the lilies the true time is obtained.

At whatever time of the day the observation is made the true time has only to be reduced to the ineau time, (by the equation of time, furnished in any little work ou epliemeris,) and this mean time to be compared with that of the first meridian, to have the exact longitude of the place.

During the observation of mid-day the north and south line of the compass-face, traced on the board N, is'directe'd in the exact direction of the meridian, and, by placing a compass at the side, the variation ot' the compass is obtained,

To obtain on board a ship a stability sillcient to assure the constant hoi'iaoiital posit-ion ot' the base ot' the instrument, in short, to neutralize the effect ofthe movements ot' the ship, recourse has been had to the double balance multiplied and combined, (see Fie. XI,) which, however, does not make a part of the instru nient.

Ais a board with tail-piece, and tolerably heavy, (shown Fig. XII.)

a is a piu, upon which the instrument can be fixed at will by means of a hole pierced in the base for this purpose.

At the center of gravity ot' the instrument b b are pins, upon which rests and pivots the hoard.

B is a circle of metal which surrounds the boa-rd; inside it is provided at b b'with two fixed notches t) receive the pins ot' the board outside with two pins, c c', whose axis cuts the axis of suspension, b b', ofthe board at right angles.

C D E F G are circles fittingintooneanother, their suspension play is in opposition, like the first inentioned, only that the axis ot the circles D and F eutting one another at right angles, cut the others atangies 'of 450, they are intended to neutralize the effects ot the diagonal movements combined ti'om sideto side or from head to stern. r

Having thus described the said invention and the nia-nner ot' perlbrniing the saine, I' would lhave it un- I derst-ood I do not contine myself' to the precise details herein indicated and represented in the drawing, as these may obviously be modified without departing from theprluciple of thesaid invention; but

That I. claim is- In connection with a box, A, having one or more semicyliudrical graduated dials provided with iiidicating-wires, and a compass, N, and levels n n, one or more stationary or movable alidades, Gr H M, provided with suitable indicators aud dials B h g, substantially as described, and t'or the purposes set fort-li.

F. M, PANNETRAT,

Witnesses H. BONNEVILLE, H. NORTON.

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