1781. _Phil. Trans._, vol. lxxi.--Astronomical Observations on the Rotation of the Planets on their Axes, made with a View to decide whether the Daily Rotation of the Earth be always the same.--On the Comet of 1781, afterwards called the _Georgium Sidus_.

1782. _Phil. Trans._, vol. lxxii.--On the Parallax of the Fixed Stars.--Catalogue of Double Stars.--Description of a Lamp Micrometer, and the Method of using it.--Answers to the Doubts that might be raised to the high magnifying Powers used by Herschel.

1783. _Phil. Trans._, vol. lxxiii.--Letter to Sir Joseph Banks on the Name to be given to the new Planet.--On the Diameter of the Georgium Sidus, followed by the Description of a Micrometer with luminous or dark Disks.--On the proper Motion of the Solar System, and the various Changes that have occurred among the Fixed Stars since the Time of Flamsteed.

1784. _Phil. Trans._, vol. lxxiv.--On some remarkable Appearances in the Polar Regions of Mars, the Inclination of its Axis, the Position of its Poles, and its Spherodal Form.--Some Details on the real Diameter of Mars, and on its Atmosphere.--a.n.a.lysis of some Observations on the Const.i.tution of the Heavens.

1785. _Phil. Trans._, vol. lxxv.--Catalogue of Double Stars.--On the Const.i.tution of the Heavens.

1786. _Phil Trans._, vol., lxxvi.--Catalogue of a Thousand Nebulae and Cl.u.s.ters of Stars.--Researches on the Cause of a Defect of Definition in Vision, which has been attributed to the Smallness of the Optic Pencils.

1787. _Phil. Trans._, vol. lxxvii.--Remarks on the new Comet.--Discovery of Two Satellites revolving round George"s Planet.--On Three Volcanoes in the Moon.

1788. _Phil. Trans._, vol. lxxviii.--On George"s Planet (Ura.n.u.s) and its Satellites.

1789. _Phil. Trans._, vol. lxxix.--Observations on a Comet.

Catalogue of a Second Thousand new Nebulae and Cl.u.s.ters of Stars.--Some Preliminary Remarks on the Const.i.tution of the Heavens.

1790. _Phil. Trans._, vol. lx.x.x.--Discovery of Saturn"s Sixth and Seventh Satellites; with Remarks on the Const.i.tution of the Ring, on the Planet"s Rotation round an Axis, on its Spherodal Form, and on its Atmosphere.--On Saturn"s Satellites, and the Rotation of the Ring round an Axis.

1791. _Phil. Trans._, vol. lx.x.xi.--On the Nebulous Stars and the Suitableness of this Epithet.

1792. _Phil. Trans._, vol. lx.x.xii.--On Saturn"s Ring, and the Rotation of the Planet"s Fifth Satellite round an Axis.--Mixed Observations.

1793. _Phil. Trans._, vol. lx.x.xiii.--Observations on the Planet Venus.

1794. _Phil. Trans._, vol. lx.x.xiv.--Observations on a Quintuple Band in Saturn.--On some Peculiarities observed during the last Solar Eclipse.--On Saturn"s Rotation round an Axis.

1795. _Phil. Trans._, vol. lx.x.xv.--On the Nature and Physical Const.i.tution of the Sun and Stars.--Description of a Reflecting Telescope forty feet in length.

1796. _Phil. Trans._, vol. lx.x.xvi.--Method of observing the Changes that happen to the Fixed Stars; Remarks on the Stability of our Sun"s Light.--Catalogue of Comparative Brightness, to determine the Permanency of the l.u.s.tre of Stars.--On the Periodical Star _a_ Herculis, with Remarks tending to establish the Rotatory Motion of the Stars on their Axes; to which is added a second Catalogue of the Brightness of the Stars.

1797. _Phil. Trans._, vol. lx.x.xvii.--A Third Catalogue of the comparative Brightness of the Stars; with an Introductory Account of an Index to Mr. Flamsteed"s Observations of the Fixed Stars, contained in the Second Volume of the Historia Coelestis to which are added several useful Results derived from that Index.--Observations of the changeable Brightness of the Satellites of Jupiter, and of the Variation in their apparent Magnitudes; with a Determination of the Time of their rotary Motions on their Axes, to which is added a Measure of the Diameter of the Second Satellite, and an Estimate of the comparative Size of the Fourth.

1798. _Phil. Trans._, vol. lx.x.xviii.--On the Discovery of Four additional Satellites of the Georgium Sidus. The retrograde Motion of its old Satellites announced; and the Cause of their Disappearance at certain Distances from the Planet explained.

1799. _Phil. Trans._, vol. lx.x.xix.--A Fourth Catalogue of the comparative Brightness of the Stars.

1800. _Phil. Trans._, vol. xc.--On the Power of penetrating into s.p.a.ce by Telescopes, with a comparative Determination of the Extent of that Power in Natural Vision, and in Telescopes of various Sizes and Constructions; ill.u.s.trated by select Observations.--Investigation of the Powers of the Prismatic Colours to heat and illuminate Objects; with Remarks that prove the different Refrangibility of radiant Heat; to which is added an Inquiry into the Method of viewing the Sun advantageously with Telescopes of large Apertures and high magnifying Powers.--Experiments on the Refrangibility of the Invisible Rays of the Sun.--Experiments on the Solar and on the Terrestrial Rays that occasion Heat; with a comparative View of the Laws to which Light and Heat, or rather the Rays which occasion them, are subject, in order to determine whether they are the same or different.

1801. _Phil. Trans._, vol. xci.--Observations tending to investigate the Nature of the Sun, in order to find the Causes or Symptoms of its variable Emission of Light and Heat; with Remarks on the Use that may possibly be drawn from Solar Observations.--Additional Observations tending to investigate the Symptoms of the variable Emission of the Light and Heat of the Sun; with Trials to set aside darkening Gla.s.ses, by transmitting the Solar Rays through Liquids, and a few Remarks to remove Objections that might be made against some of the Arguments contained in the former paper.

1802. _Phil. Trans._, vol. xcii.--Observations on the two lately discovered celestial Bodies (Ceres and Pallas).--Catalogue of 500 new Nebulae and Cl.u.s.ters of Stars, with Remarks on the Construction of the Heavens.

1803. _Phil. Trans._, vol. xciii.--Observations of the Transit of Mercury over the Disk of the Sun; to which is added an Investigation of the Causes which often prevent the proper Action of Mirrors.--Account of the Changes that have happened during the last Twenty-five Years in the relative Situation of Double Stars; with an Investigation of the Cause to which they are owing.

1804. _Phil. Trans._, vol. xciv.--Continuation of an Account of the Changes that have happened in the relative Situation of Double Stars.

1805. _Phil. Trans._, vol. xcv.--Experiments for ascertaining how far Telescopes will enable us to determine very small Angles, and to distinguish the real from the spurious Diameters of Celestial and Terrestrial Objects: with an Application of the Result of these Experiments to a Series of Observations on the Nature and Magnitude of Mr. Harding"s lately discovered Star.--On the Direction and Velocity of the Motion of the Sun and Solar System.--Observation on the singular Figure of the Planet Saturn.

1806. _Phil. Trans._, vol. xcvi.--On the Quant.i.ty and Velocity of the Solar Motion.--Observations on the Figure, the Climate, and the Atmosphere of Saturn and its Ring.

1807. _Phil. Trans._, vol. xcvii.--Experiments for investigating the Cause of the Coloured Concentric Rings, discovered by Sir Isaac Newton between two Object-gla.s.ses laid one upon another.--Observations on the Nature of the new celestial Body discovered by Dr. Olbers, and of the Comet which was expected to appear last January in its Return from the Sun.

1808. _Phil. Trans._, vol. xcviii.--Observations of a Comet, made with a view to investigate its Magnitude, and the Nature of its Illumination. To which is added, an Account of a new Irregularity lately perceived in the Apparent Figure of the Planet Saturn.

1809. _Phil. Trans._, vol. xcix.--Continuation of Experiments for investigating the Cause of Coloured Concentric Rings, and other Appearances of a similar Nature.

1810. _Phil. Trans._, vol. c.--Supplement to the First and Second Part of the Paper of Experiments for investigating the Cause of Coloured Concentric Rings between Object-gla.s.ses, and other Appearances of a similar Nature.

1811. _Phil. Trans._, vol. ci.--Astronomical Observations relating to the Construction of the Heavens, arranged for the Purpose of a critical Examination, the Result of which appears to throw some new Light upon the Organization of the Celestial Bodies.

1812. _Phil. Trans._, vol. cii.--Observations of a Comet, with Remarks on the Construction of its different Parts.--Observations of a Second Comet, with Remarks on its Construction.

1814. _Phil. Trans._, vol. civ.--Astronomical Observations relating to the Sidereal Part of the Heavens, and its Connection with the Nebulous Part; arranged for the Purpose of a critical Examination.

1815. _Phil. Trans._, vol. cv.--A Series of Observations of the Satellites of the Georgian Planet, including a Pa.s.sage through the Node of their Orbits; with an Introductory Account of the Telescopic Apparatus that has been used on this Occasion, and a final Exposition of some calculated Particulars deduced from the Observations.

1817. _Phil. Trans._, vol. cvii.--Astronomical Observations and Experiments tending to investigate the Local Arrangement of the Celestial Bodies in s.p.a.ce, and to determine the Extent and Condition of the Milky Way.

1818. _Phil. Trans._, vol. cviii.--Astronomical Observations and Experiments selected for the Purpose of ascertaining the relative Distances of Cl.u.s.ters of Stars, and of investigating how far the Power of Telescopes may be expected to reach into s.p.a.ce, when directed to ambiguous Celestial Objects.

1822. _Memoirs of the Astronomical Society of London._--On the Positions of 145 new Double Stars.

The chronological and detailed a.n.a.lysis of so many labours would throw us into numerous repet.i.tions. A systematic order will be preferable; it will more distinctly fix the eminent place that Herschel will never cease to occupy in the small group of our contemporary men of genius, whilst his name will reecho to the most distant posterity. The variety and splendour of Herschel"s labours vie with their extent. The more we study them, the more we must admire them. It is with great men, as it is with great movements in the arts, we cannot understand them without studying them under various points of view.

Let us here again make a general reflection. The memoirs of Herschel are, for the greater part, pure and simple extracts from his inexhaustible journals of observations at Slough, accompanied by a few remarks. Such a table would not suit historical details. In these respects the author has left almost every thing to his biographers to do for him. And they must impose on themselves the task of a.s.signing to the great astronomer"s predecessors the portion that legitimately belongs to them, out of the ma.s.s of discoveries, which the public (we must say) has got into an erroneous habit of referring too exclusively to Herschel.

At one time I thought of adding a note to the a.n.a.lysis of each of the ill.u.s.trious observer"s memoirs, containing a detailed indication of the improvements or corrections that the progressive march of science has brought on. But in order to avoid an exorbitant length in this biography, I have been obliged to give up my project. In general I shall content myself with pointing out what belongs to Herschel, referring to my _Treatise on Popular Astronomy_ for the historical details. The life of Herschel had the rare advantage of forming an epoch in an extensive branch of astronomy; it would require us almost to write a special treatise on astronomy, to show thoroughly the importance of all the researches that are due to him.

FOOTNOTE:

[17] These t.i.tles are copied direct from the Philosophical Transactions, instead of being retranslated.--_Translator"s Note_.

IMPROVEMENTS IN THE MEANS OF OBSERVATION.

The improvements that Herschel made in the construction and management of telescopes have contributed so directly to the discoveries with which that observer enriched astronomy, that we cannot hesitate to bring them forward at once.

I read the following pa.s.sage in a Memoir by Lalande, printed in 1783, and forming part of the preface to vol. viii. of the _Ephemerides of the Celestial Motions_.

"Each time that Herschel undertakes to polish a mirror (of a telescope), he condemns himself to ten, or twelve, or even fourteen hours" constant work. He does not quit his workshop for a minute, not even to eat, but receives from the hands of his sister that nourishment without which one could not undergo such prolonged fatigue. Nothing in the world would induce Herschel to abandon his work; for, according to him, it would be to spoil it."

The advantages that Herschel found in 1783, 1784, and 1785, in employing telescopes of twenty feet and with large apertures, made him wish to construct much larger still. The expense would be considerable; King George III. provided for it. The work, begun about the close of 1785, was finished in August, 1789. This instrument had an iron cylindrical tube, thirty-nine feet four inches English in length, and four feet ten inches in diameter. Such dimensions are enormous compared with those of telescopes made till then. They will appear but small, however, to persons who have heard the report of a pretended ball given in the Slough telescope. The propagators of this popular rumour had confounded the astronomer Herschel with the brewer Meux, and a cylinder in which a man of the smallest stature could scarcely stand upright, with certain wooden vats, as large as a house, in which beer is made and kept in London.