vided with an "arming" which will be as significant | 4th. The Prime Vertical Transit Instrument, to the Astronomer of what it has encountered in Pistor & Martins, Berlin. Observers, W. A. the depths of space, as is of the depths of the Wayne, Lieut. U. S. N., and James Johnson Pitocean, the sand to the mariner which adheres to his tigrew, a young Mathematician from N. Carolina. lead. 5th. The Equatorial, Murz & Mahler, Munich. Occasional Observers, myself and Joseph S. Hubbard, Professor of Mathematics, U. S. N. But so far from its expected appearance, in 1848, being cause of dread and alarm to Powers and Potentates, its coming is looked for even by the multitude, with a degree of eager interest and will be hailed with pleasure and delight in many lands. 6th. The great "Refraction Circle," Ertel & Son, Munich. Observers, none. Lieut. Page is in daily expectation of orders to sea, and Lieut. Steedman has been in training to take his place at the Mural. Hence the names of three officers for that Instrument. Professor Hubbard has been recently detailed for duty not connected with the Observatory. When he returns, he will observe regularly with the Equatorial. As soon as practicable I propose also to place professor Keith at the Refraction Circle. From a mysterious messenger, bringing tidings of a dreadful, potent and awful calamity to a terrorstricken world, Astronomy by its progress has changed in the minds of men the character of comets; they have been made obedient to law, subservient, instructive and useful to man, in his upward and onward progress. They teach important troths, and assist to reveal the secrets of nature. You, yourself, may recollect the time when Astronomers were called upon to quiet the public mind iu one of the most refined capitals of Europe, and soothe the dreadful apprehensions with which the approach of a comet was regarded. Yet even during the short interval, such has been the activity Considering that the expense of buildings, piers and the progress in this department of science, that and instruments has already been incurred for this comets have ceased to be regarded as objects of Observatory,—it is obviously more in conformity terror sent, at long intervals, to warn or to punish; they are rather looked upon as fellow-travellers and instructive companions to man in his journies through space. Instead of years, scarcely a month now elapses without the announcement that some new comet has been discovered; such is the activity of research. The people of America have caught up the spirit, and are beginning actively to engage in Astronomical pursuits.* You have had the subject, as far as this country is concerned, anxiously at heart for years wherefore I consider the present occasion as one for congratulation. Pardon, therefore, the digression. It is a rule among Astronomers to consider an additional assistant at an Observatory which has as many as two observers already employed, to be worth more than two better men at a new Observatory. with the principles of true economy to apply force enough to give the instruments full occupation whenever the weather will admit, than to have them only half manned, or feebly served. Accordingly I have constantly aimed to have at least two observers for each instrument; so that when the night is clear there may always be an eye for every Telescope in the Observatory. But the unusual demand for officers afloat on the one hand and their anxiety for war service on the other, have made it difficult, during the last year, to keep at the Observatory its full compliment of observers. The West Transit instrument is mounted on the The Astronomical Instruments of the Observa- Meridian in the West wing of the Observatory. tory, with Telescopes attached, are six. The reg-It has an object glass of 5.4 inches aperture, with a ular Observers, eight. focal length of 7 feet 1 inch. A clock is an indispen 1st. The West Transit Instrument, made by sable companion of this instrument, as a time-keeper Ertel & Son, of Munich. Observers, Mark H. of some sort is of every Astronomical Telescope. Beecher and Ruel Keith, Professors of Mathema- The clock is a mercurial pendulum, by Parkinson tics, U. S. N. and Frodsham. 2nd. The Mural Circle, made by Tunghton & Simms, London. Observers, Thomas J. Page and Charles Steedman, Lieutenants, and J. H. C. Coffin, Professor of Mathematics, U. S. N. 3rd. The Meridian Circle, Ertel & Son. Observers, William T. Muse, Lieutenant, and James Major, Professor of Mathematics, U. S. N. The Transit instrument affords data for the determination of Right Ascensions. By it time is determined-clocks rated, etc. The Mural Circle, with the Meridian Circle, is mounted in the East wing. It is 5 feet in diameter and has a Telescope with an object glass of 4.1 inches aperture, and 5 feet focus. The Mural Circle is for the determination of Declinations. By it Latitude is also determined. The last Comet was first discovered by a lady of your The Meridian Circle has a Microscope Bearer own State-(Miss Mitchell of Nantucket.) She has also with 4 Microscopes; and 2 circles of 30 inches di computed its orbit. Thus Maria Mitchell's Comet is ano ther evidence of the attention which the subject of Astron-ameter, one for degrees and minutes, and the other omy is exciting in this country. for seconds, connected with a telescope of 3.8 inches aperture, and 4 feet 11 inches focal length. mercurial pendulum, Charles Frodsham. clock answers also for the Mural. Clock, | serving only as the object to be observed crosses This instrument unites the transit instrument and the Mural Circle. It is for the determination of both co-ordinates. The object of the Equatorial is to observe occultations and eclipses, to determine the places of The Prime Vertical Transit Instrument, is moun- comets and planets by differential measurements. ted on the Prime Vertical in the first apartment of It is also used for measuring the angular disthe South wing. It has no circle except a finder.tance and position between double stars, for meaThe telescope has a focal length of 6 feet and suring the diameters of planets, etc. It may be 4.8 inches aperture. Clock, grid-iron pendulum, turned for observations at any time upon any object Charles Frodsham. in whatever part of the visible heavens. Its greater This instrument is also for the determination of optical and space-penetrating powers, invest its laRight Ascensions and Declinations. But while it is bors in physical Astronomy with exceeding intercapable of a higher degree of accuracy than any est and give it other advantages, which are not one of the aforementioned instruments, it is confin- possessed by its more humble companions below, ed to a more narrow field; it works more slowly; though for differential position it is subsidiary to and cannot compete with its compeers in number and dependent upon their determinations. or subjects of observation. They can observe all The Refraction Circle has two Microscope Bearobjects that appear above the horizon and cross the ers, which carry six microscopes each; two gradmeridian-it, those only which cross its prime ver-uated circles of four feet each, with divisions for tical-which in this instance embraces those stars whose parallels of Declination are included between the Equator and the Zenith of this Observatory. every 2' of arc on gold; and a Telescope of 5.8 inches clear aperture and eight and a half feet focal length. This instrument is new in its combinations The Declinations determined with this instru- and construction. It unites the exquisite accuracy ment are surprisingly accurate. It is capable of of the Prime Vertical Transit instrument, with all affording results possessed of a higher degree of the advantages, compass, and capabilities of the accuracy perhaps than those obtained from any Mural Circle and Zenith Sector. It is the first of other instrument at present known to Astronomy. its kind ever made, and was constructed from plans This is in part owing to physical and mathematical advantages derived from its position in the prime vertical, and partly to mechanical and instrumental peculiarities. It is a new instrument; It was invented by the direction of the Central Observatory of Russia, and this is the only other instrument of the kind except his. and drawings prepared at this Observatory. The makers pronounce it to be the most complete astronomical instrument that has ever left their hands. Its performance, however, remains to be tried. Equally adapted for mounting on the Meridian or the Prime Vertical, it surpasses all the first four mentioned instruments for power and compass: Its position frees its results from and makes them and in means for imparting accuracy to results, it independent of the effects and uncertainties of at-possesses advantages which none of them have. mospherical refraction, and of the numerous im- It is situated in the second apartment of the perfections and sources of error to which instru- South wing, which has been extended to receive ments with graduated arcs and circles are liable. it. It is, at present, mounted on the Prime VertiIts peculiar construction and extraordinary facilities of reversal, neutralize other instrumental imperfections which are, also, fruitful sources of error whenever their effects remain for the skill and patience of the observer to detect and expose. It is particularly well adapted for investigating the problem of Stellar Parallax. cal, but its ultimate destination is the Meridian. It is the only Astronomical instrument which has ever been constructed and mounted, that independent of any previous hypothesis is capable of determining directly and immediately the effect of atmospherical refractions in optically displacing the heavenly bodies. It is the first instrument The equatorial has an object glass of 9.6 inches ever used on this continent for the investigation aperture and fourteen and a half feet focal length. of this most important problem; it will begin these It is provided with clock work for siderial motion, investigations on the Prime Vertical and end and the observations are timed from a siderial chro-them on the Meridian. Hence it is called the nometer rated by the clocks below. It rests in the REFRACTION CIRCLE, though there are many other dome, and surmounts a massive block of granite subjects and problems towards the affording of which is supported by a conical pier of brick work, data for the solution or investigation of which it is rising from the foundation of the building and pass-equally well adapted. ing up in isolation of the floors and all other parts of the Observatory. Theory points to perturbations by the moon and planets upon the earth's centre of gravity. These Each one of the other instruments moves in the daily disturbances, except as their effects are explane of but one great circle, and is capable of ob- 'hibited by the tides of the ocean, or marked by the Barometer, have never, that I am aware of, been on the side opposite the first. Thus the maximum made the subject of direct observation. deviation will be multiplied four times, and so mul The facility with which the instrument is reversed and the manner in which it is supported on its pier, will impart to its results, a degree of confidence as to accuracy of determination that but few instruments have ever afforded. This instrument, therefore, suggests a class of tiplied, will be brought under the highest magnifying observations entirely new. And it is proposed to powers of the instrument for detection and obserundertake them; for, whether successful or not, vation. the experiment will not be needless; but in either event will be possessed of both interest and value. In consequence of the influence of the moon and other bodies, the centre of attraction of the earth may be supposed to revolve about its geometrical centre. It may be that this instrument is capable of determining, by actual observation, the orbit which one of these centres makes about the other; for, by an optical artifice, the centre of attraction, so to speak, or, which is the same thing, (the nadir point, which is in a line with this centre,) may be rendered visible; it only remains to be seen whether this instrument have powers sufficient to detect its minute changes. Permit me to explain— But it would be altogether out of place and premature to discuss its powers here, or to anticipate results. I, therefore, pass on to the other subjects upon which you desire information. According to the British Association for the advancement of science, the vast sums of money which have been spent by Astronomers in doing over again what has been better done elsewhere, in determining Astronomical data, might have almost created new sciences of observation. Not to make this Observatory liable to such a charge, a plan has been adopted for its labors which, while the plan seeks to avoid doing over again what has already been well done, aims at results both useful to the world and creditable to the country. The general outlines of this plan are to keep up a regular and systematic series of observations upon the sun, moon and planets and certain fundamental stars, with the view of procuring data for the American Nautical Almanac. But the Observers and instruments are capable of many more observations than these; and with the views of fully occupying the time of each, I, at an early day, proposed regularly and systematically to penetrate, with our excellent Telescope, every point of space in the visible heavens, with the view of assigning position and magnitude, and of cataloguing every star, cluster, nebulae or object that should pass through the field of view. By turning the Telescope down upon a basin of of mercury, the image of the spider-thread, which is placed in the stellar focus of the object glass of the Telescope, may be seen as though it were an object at an infinite distance. Resorting to this optical artifice, by which the most attenuated line is placed in the nadir and directly in a line with the centre of gravitation, and taking advantage of the peculiar and extraordinary collimating powers of this instrument, it will be impossible for any deviation of the plummet amounting on the surface of the earth to as much as the breadth of the finest gossamer, from its normal state, to escape observation. Permit me to illustrate by an example: Suppose the moon to be on the meridian at its lower culmination, and that the spider line in the the focus of the Telescope be made to occult its own image over a basin of mercury and as seen in the nadir, we shall then have the most perfect plummet that can be dropped. The position of the Telescope is then noted, and in this position it remains. Suppose now after the moon rises, and reaches that altitude in the East at which her disturbance of the plummet is a maximum, that the Telescope is again examined and the spiderthread and its image found to be no longer in occultation. This, assuming stability in all other re- The plan originally contemplated and designed spects to be perfect, will be owing to the fact, that is to sweep over the same belt twice, but not on the centre of attraction has changed its position, the same night, nor with the same instrument or and passed, also, to the East of the geometrical observer. Supposing the conditions of atmosphere, centre, so to speak, of the earth, and, in conse- instrument and eye to be the same, all the stars, quence, the mercury in the basin has adapted itself to this new centre, and, therefore, changed its inclination, by an amount equal to the deflection that would be produced upon the plummet. The maximum effect of this change, being seen by reflection, is apparently doubled. Leave was sought and readily granted to carry this plan into effect, and the labor of near two years has already been expended upon it. A catalogue of about 1,200 stars, most of thein unknown to existing catalogues, is the result of the first year's work in this field. and no more, which are observed during the first sweep, should be observed during the second. The work in this case is complete. But suppose, and this is generally the case, that stars are observed in one sweep which are not observed in the other, the Equatorial is then turned When the moon reaches a like altitude West, upon the same belt to reconcile discrepancies; so the same takes place. But, in this instance, the that no star may be entered in the catalogue withimage appears to the West, instead of the East of out having been made the subject of observation the real thread, and the effect is again doubled, but at least twice, and each time on a different occa sion, by a different instrument and observer. In addition to this, the plan, as originally designed, contemplates measures of distance and angle of position upon all double or multiple stars, accurate drawings and descriptions of all clusters and nebulae. No Astronomical work on such an extensive scale has ever been executed or attempted. The value and importance of it are manifold, but difficult of full estimation. kind in the world, and the largest that it has hitherto been thought possible to construct, has an object glass of but 18 inches in diameter. That of this Observatory has an object glass of only 9 inches, and there are two others in the country nearly or quite double the size of this. The celebrated opticians and principal makers of refracting Telescopes, Merz & Son of the Fraunhoffer establishment, who have been consulted on the subject, are willing to risk their character and The intention is to make a contribution to As-reputation as the most renowned makers in the tronomy worthy of the nation and the age, and so world, upon an object glass of 24 inches clear aperto execute the undertaking, that future Astrono- ture. They have made the liberal offer of such an mers in all time may say of it, such a star was not instrument for $120,000. And it will require four visible in the heavens at the date of the Washing- or five years to complete it. I hazard but little ton Catalogue, because it is not there, and such a in saying that a Telescope of this description, star that is now missing, was in the heavens be- made with the usual skill and success of these cause it is in that work. celebrated makers, would surpass all others in its astronomical performances. It would be regarded by practical Astronomers and those engaged in the researches of Physical Astronomy as the most superb instrument in the world. And what would be the cost of such an instrument to the people of the United States? Only a half of a cent per head. Such, at least, is the point aimed at. How far we shall fall short of it remains for results to show. These are the principle subjects of observations. There are many others; but to recount them would make my letter tedious, I therefore pass them by. Great undertakings, such as is this Catalogue, whose value and importance are confined to no country and limited to no age, are beyond the power of Astronomers working single-handed. They require a large force and abundant facilities, such as individuals cannot afford, and therefore fall peculiarly within the province and duties of government. It is to be a contribution to science worthy of a great nation. It is to extend beyond the age in which we There is no department of science which is more live. and reach posterity with lasting benefits. If intimately connected than Astronomy, with the intherefore, a grand Catalogue be undertaken at all, no terests whether of government or people. By Aslabor should be spared for giving it weight and au-tronomy the length of the year is established, the thority in all time to come; all facilities, means and rising and setting of the sun are calculated, and time appliances should be afforded the Observatory, which itself, in all its relations, is measured, fixed, or deare calculated to give useful embellishment to such termined. The man of business, when he looks at a work, to impart interest, or add to its value. To his watch for the hour, is as much indebted to Asmake it complete researches in the higher depart-tronomy for the ability punctually to fulfil his enments of physical Astronomy are wanted. These gagements as the farmer, when he consults his cannot be conducted in the manner the most sat- almanac for the phases of the moon. isfactory to the world and creditable to the nation, without the aid of a more powerful Telescope than any which the Observatory now has. They are enlightened, free and intelligent, and would they, think you, when they are reminded of the practical importance and value of Astronomy in the daily affairs of life, whether, as between man and man, or nation and nation, grudge an appropriation for such a purpose? There is a strong and commendable feeling of national pride among the people of the United States. Whatever the country undertakes to do, they desire to see well done. I have reason to believe that this feeling obtains as strongly with regard to the Observatory, now that it is in operation, as it does with regard to any other subject whatever. I refer with pride to this trait in the character of the American people, for it causes them to desire never in National undertakings to be behind other countries. When a boundary line is to be established between this country and a neighboring nation, or between State and State of the confederacy, it is done by Astronomy. The latitudes and longitudes of lines and points, on the earth, are determined by the positions of the stars or other bodies, as we find them recorded by European Observers. If there be mistakes in the declinations which they assign to stars, there will be also like mistakes in the latitude which we determine from them, and it would be quite as consistent, with true national self-respect, to send for European surveyors to run our boundary lines, as it is to look to European Astronomers to determine for us the true positions of the stars, without the positions of which stars, those boundaries could not be run. Accordingly, I have consulted the most celebrated artists of Europe as to the cost and size of the largest Refracting Telescope equatorially mounted, Without the guides and helps of astronomy that can be made. The largest Telescope of the' which have been kindly and gratuitously furnished by other nations, we could have no navy, no ships, I will merely mention that the Nautical Almanac no commerce, or if we had, our ships could never venture across the ocean or out of sight of our own shores. But for the Nautical Almanac of England or other European countries, and the labors of their Observatories and astronomers, the American ships, now abroad, could not find their way home. But for the principles of practical Astronomy, the metes and bounds of landed estates could neither be recovered nor preserved. It is true the lines of a survey are run by the compass, but the compass is not true, nor stable. Its errors can be detected only according to astronomical investigations. The needle neither points to the pole, nor in the same direction for any length of time. It is always varying; and the amount of such variation is the subject for astronomical determination. should be computed and published, at least three years in advance, so that ships, departing on long cruises, may be furnished with a copy. That it is a work which requires much labor and great care in the preparation; for any, the slightest error or mistake, may prove disastrous both to property and life in all parts of the world. The superintendent of the Observatory could not undertake to superintend the Nautical Almanac, in detail, without wholy neglecting his other and equally important duties. He might, indeed, have the general direction of it, so far as to say what it should contain, from what sources the materials to be embodied in it should be obtained, and what tests, examinations and proofs it should undergo in the preparation, etc. But there should be a special and subordinate Superintendent of the Nautical Almanac, whose duties should be confined to the details of the work and to nothing else. He will require the assistance of a small corps of computors; for every calculation should be repeated at least twice, and by at least two computors, each working indepen. dent of and without the knowledge of the results obtained by the other. I have a letter, now before me, from a surveyor in a neighboring state, informing me that the landmarks of a survey run, a century since, and which he has now to run over, have been obliterated. But he states his compass-courses and asks for information to enable him to determine what they 10w should be, to reproduce the same lines. SimIn the foregoing account, are included only a ilar calls are, by no means, unusual. Considering their frequency and importance, I may be excused portion of the duties performed at this office and for suggesting here a law in every state, requiring mention has been made of but a part of the force engaged. for the benefit of posterity, that, hereafter, all deeds of conveyance in which the metes and bounds of real estate are set forth or described, should expressly state the variation of the compass at the time of the survey. The Observatory is, literally, also a "Depot" of charts and instruments for the Navy. Here charts are purchased, prepared and distributed; nautical books supplied, instruments, etc. We take a weight, or measure a rod, and call the furnished to our public vessels. Before a chroone a pound, the other a yard. But use, decay, nometer is purchased here for the Government, it time, and heat, produce their effects, and these is taken on trial for a year, during which time it is measures are altered, changed and lost forever. carefully compared with a standard clock, that a If preserved in their tangible shape, they are no record may be kept of its performances, which reclonger of the same value. But Astronomy fur-ord is required with the utmost nicety, and emnishes an invariable unit for weight and measure braces the hundredth part of a second. There are which never changes; and nations are continually in some sixty or eighty chronometers alone in the the habit of consulting it for the benefit of their office whose rates are kept with such care. Bepeople. Every person, therefore, who buys and sides these there are numerous other instruments sells by just and lawful measure, is enabled to do which demand much attention. so only in consequence of Astronomical determinations--so intimately are the principles of this science interwoven with the business affairs of men and nations, in their political, social and civil relations. The reasons and considerations which call for the establishment of national standards of weights and measures, call with like force, propriety and urgency for a national standard of Astronomical results. These results are comprehended in the term, and included in the work, styled, THE NAUTICAL ALMANAC. The advantages and importance of such a work are obvious. It is unnecessary to point to them here. VOL. XIV-2 There is, also, much hydrographical duty to be performed: Charts are to be corrected or compiled; and the undertaking has been commenced here of preparing "wind and current" charts of the three grand oceans, viz: the Atlantic, the Pacific, and Indian. These charts are intended to generalize the experience of navigators in such a manner that each may have before him, at a glance, the experience of all. The track of each showing the time of the year, the prevailing winds and currents encountered, with all other information obtained is projected on the charts. The first sheet, of which there are 8, of the Atlantic, drawn by William B. Whiting, Lieut. U. S. Navy, has already been pub |