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the tables of Mayer, which were the first generally available for nautical longitudes; 3,000 were employed by Burg for his tables, which so completely satisfied the conditions of a prize for such tables offered by the Consular Government of France, that the First Consul doubled the prize; and of the 4,000 which were employed by Burckhardt to correct the lunar elements for his famous tables (which served for nearly fifty years prior to 1862 as the basis for all navigational predictions), nearly the whole must have been derived from Greenwich.

The great lunar reductions previously alluded to embraced nearly 9,000 Greenwich observations of the moon, made between the years 1750 and 1830-a series without a parallel. The first fruit of their reduction was a general correction by Sir George Airy of the received elements of the moon's orbit. The next was the discovery by Prof. Hansen, of Gotha, of two inequalities of long period in the moon's motion, depending upon the direct and indirect action of the planet Venus. And what may be considered for the present as the ultimate outcome, was the construction by Hansen of the great Lunar Tables that bear his name, which represent the motions of our satellite with an accuracy surpassing all others, and abundantly sufficient for the preparation of reliable nautical ephemerides. Hansen's tables are used for all the important "Nautical Almanacs" of the world, with one exception, that of America, for which special tables were previously prepared, embodying, however, the corrections derived from the long suite of Greenwich observations.

If we look to other planetary tables, we find the same dependence for their data upon our National Observatory. The tables now used for Jupiter, Saturn and Uranus are those by Bouvard (1821), and they depend mainly upon the observations of those planets by Bradley, Maskelyne and Pond. The tables of Mercury, Venus, and Mars are Le Verrier's, based chiefly upon the Greenwich observations from 1750 to 1830, which were, with the rest of the planetary observations for that period, reduced by Sir George Airy en masse, like the lunar observations. For the sun, Le

Verrier's Tables are also used; and they depend upon a century's Greenwich observations. The current tables of Neptune are those by Professor Newcomb, for which Greenwich found the major part of the observational data. Throughout the whole series of Planetary Tables that belong to the period of accurate astronomy, there is such a broad reliance for data upon Greenwich, and such comparatively small support derived from other places, that it is evident there was no excessive flattery in Baron Zach's assertion that our astronomical tables would have been as perfect as they are if no other observatory had ever existed. All this we adduce, not with the idea of glorifying a

national institution, but merely to aid the full conception of its mission, which was defined in Sir John Herschel's always happy words to be "to furnish now and in all future time the best and most perfect data by which the laws of the lunar and planetary movements as developed by theory can be, compared with observations."

It will be easily seen that with all things organised to this end there is little room for such work as double-star measures, celestial photography, delineations of planets and nebulæ, spectroscopy, &c. Some of these have occasionally been taken up for a time, but none of them have been, or indeed could be, systematically followed.

Of late, however, there has been a tendency in some subjects of this character to overrun the powers of attention of amateurs, to whom they have been left; and it has been suggested that inasmuch as they ought to be followed by the State, and Greenwich as at present constituted could not undertake the work, a special Observatory ought to be established and devoted to Astronomical Physics. The systematic record of solar phenomena (sun-spots, gaseous eruptions, &c.) has been mentioned as in immediate need of pursuit. Not unnaturally a counter question arose whether all that it was desirable for the State to undertake could not be done at Greenwich, and the Astronomer Royal laid his views upon the general question before the Board of Visitors at their meeting on June 1 last, in the following terms:

"The tendency of late discoveries and consequent discussions in astronomy has been, not to withdraw attention from the exact departments of astronomy, but to add greatly to the public interest in those which are less severely definite. And this has become so strong, that I think it may well be a subject of consideration by the Board of Visitors whether observations bearing upon some of those trains of discovery should not be included in the ordinary system of the Royal Observatory. The criteria which, as appears to me, may be properly adopted in the selection or rejection of subjects of observation are these Observations which can be made at any convenient times, which do not require telescopes of the largest size, and which do not imply constant expense, ought to be left to private observers. Observations which demand larger telescopes, and especially observations which must be carried on in continual routine and with considerable expense, can only be maintained at a public observatory. The claims of each subject must be separately considered; but there can be no doubt that a very powerful demand for attention is made when private persons have been induced to continue observations for a long time at considerable current expense, and when plausible

evidence is given of the connexion of results thus obtained with other cosmical elements. I think that these considerations exclude measures of double stars at the Royal Observatory, but they leave an opening for the scrutiny of nebulæ, planets, &c., and possibly (but I speak in doubt) of solar spectroscopy. But I have no doubt that they fully sanction the undertaking a continued series of observations of solar spots. The character of the Observatory would be somewhat changed by this innovation, but not, as I imagine, in a direction to which any objection can be made. It would become, pro tanto, a physical observatory; and possibly in time its operations might be extended still further in a physical direction."

Upon the effect of these statements it would be premature to speak. It is, however, generally understood that the Board decided upon the advisability of extending the Observatory system so far (for the present) as to include regular photographic record of solar spots and systematic solar spectroscopy. The Visitors are an intermediary body: before full effect can be given to their decision the Treasury must be appealed to for funds for the first cost of instruments and the running expense of an increased personal staff.

Chronometers have such a direct connection with navigation and sea-longitude, that not unnaturally Greenwich has been identified with the testing of these instruments from their invention to the present day; and now it is the chief depôt for Government marine chronometers. All business of their purchase, trial, and repair, is transacted at the Observatory; and usually about 200 chronometers are there under rating for issue to H.M. ships. Every year there is a competitive trial open to all makers, during which the chronometers are exposed to a wide range of temperature: four or six of the best instruments are each year purchased at good prices, and it is doubtless to these trials and to the general Government patronage of the trade that the supreme excellence of British chronometers is due.

Into the department of Time and its distribution we need not enter further than to say that a signal ball is dropped at one o'clock daily at the Observatory, and another ball at Deal is dropped by direct current from the Observatory; and that every hour accurate electric signals go forth from Greenwich, which are variously distributed over the country; one of them, that at 10 A.M., passing through well-nigh all the important telegraph lines in England. This department of the Observatory was, however, fully described in a previous number of the POPULAR SCIENCE REVIEW (October 1870).

A magnetical and meteorolgical department was established in 1840, and till 1847 eye-observations of its instruments

were made every two hours, day and night. In 1848 photographic registration was introduced, and from then till now there has been an unceasing record of the movements of the declination, horizontal force, and vertical force magnetometers, as well as of the barometer and the dry and wet bulb thermometers. The anemometers, for direction, force and velocity of the wind, and also a pluviometer, register themselves mechanically. The magnetic observations and registers to 1863 have been discussed, and the epitomised results form the subjects of various memoirs in recent volumes of the Philosophical Transactions. It may be mentioned that among other points these discussions negative the existence of a decennial magnetic period related to the period of solar spot activity. A great discussion of temperature records from 1848 to 1868 is now in progress. Within the past few years an important, and we believe unique, addition has been made to the photographic recording department. The spontaneous galvanic "earthcurrents that at times become so intense as to interfere with telegraphic operations, have been made to record themselves perpetually by reflecting galvanometers connected with special wires running in N.-S. and E.-W. directions through the Observatory, and attached to earth-plates at their extremities. A discussion of some of the registers has shown that these currents are related to the earth's magnetism in its disturbed state -as during auroral displays-but apparently not in its tranquil state.

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In conclusion, it should be stated that the Greenwich observations of all kinds are published in yearly 4to. volumes of nearly 1,000 pages each, in which every observation is set down in the utmost detail, with every instrumental reading as it is recorded by the observer, and (especially in the case of the astronomical observations) with every step in the reductions exhibited, down to the final results, which are given in such a form as to be directly available to the theoretical investigator.

283

THE RECENT FOSSIL MAN.

By J. MORRIS, F.G.S.

PROFESSOR OF GEOLOGY IN UNIVERSITY COLLEGE, London.

[PLATE LXXXVII.]

THE

HE subject of the antiquity of man has of late years attracted considerable attention, and the terms palæolithic and neolithic have become nearly as familiar as those of the stone and iron age of former years. For preconceived opinions on this point, and the apparent doubtful evidence of the association of the human species with those of the extinct mammalia, strengthened the belief of the appearance of man only after the great physical changes had brought about their disappearance. Hence arose, partly from want of careful observation, much controversy on the subject, and, although maintained by some, the opinion has been confirmed by the re-examination of several of the cases cited, as well as by recent discoveries, that the remains of man lie entombed in earlier graves than those where

The rude forefathers of the hamlet sleep.

Among those who carefully investigated and prominently brought the subject forward were Mr. Prestwich and the late Dr. Falconer, after their examination of the discoveries near Abbeville by M. Boucher de Perthes and of the Brixham cave; the facts of the contemporaneity of the works of man with the remains of extinct mammals were still contested by Elie de Beaumont and others; but the opinions of Mr. Prestwich were corroborated by Mr. Evans, Mr. Flower, Sir J. Lubbock, Sir C. Lyell, and by MM. Lartet and Christy, and Gaudry in France.

The occurrence of human remains are far more rare in caverns or other deposits than those of the works of man, and hence every additional fact is worthy of careful examination.

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