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leed, the few experiments of the French observers, and Gilbert Child and Bastian in this country are the only es at present made.

The reason is obvious, the conditions of the exriment and observation required are so difficult that - have not yet mastered them. They are first, ensure all the favouring circumstances in the labotory experiment which natural stations afford, and, course, to ensure them it is necessary to know or ve some idea (which biologists have not) as to what ey may be; second, to exclude simultaneously all living atter; third, to make the observations throughout ith the greatest minuteness which the microscope perits a necessary condition, on account of the possible nallness of particles of living matter. When we have ad experiments performed in this way with a vast variety the first-named set of conditions, so as to obtain and udy the action of various natural circumstances which night possibly be present in the de novo origination of ving from mineral matter-then we may speak of evience on the question. As it is, we have but a very complete and discordant series of observations on one lass of conditions in which there is a presumption of pontaneous generation (the case of Bacterium), and which ave been selected for experiments on account of a upposed facility for isolation, without interference with the conditions, but of which very little is understood at all. I venture to submit that this single case, in which there has been some little investigation with, be it granted, negative result, so far from warranting the enunciation of a dogma, which is declared to be as sure as a great law expres-sing the concurrence of almost infinitely numerous, varied, and reiterated observations, does not even justify an opinion; it has no possible bearing upon the source of the minute protoplasmic particles which the microscopist finds abundantly in sea-water, nor upon the origin of the atmospheric germs which are so largely invoked by some persons. It leaves us necessarily to a priori considerations in regard to the origin of life on the earth, and until direct researches are made, the hypothesis developed by a priori argument must have far more claim on the adbesion of an unbiassed mind, than a pseudo-law, though the latter bear an authority so great in some departments of science as is that of Sir William Thomson.

E. RAY LANKESTER

RECENT FRENCH ZOOLOGICAL DISCOVERIES
TWO
WO naturalists, who have been more than usually
successful in their investigations of the faunas of
distant and little-known countries, have recently returned
to France, and are now engaged in working out the results
of their arduous expeditions. These are M. le Père
Armand David, and M. Alfred Grandidier.

David during the recent exploration of Mopin, as this portion
of the Celestial Empire is termed by the French writers, have
of late years seldom been equalled in any part of the world
for extent or variety. The fauna of these mountains seems
to be a sort of pendant to that of the Himalayas, which,
some years ago, was so successfully investigated by Mr.
Hodgson. The singular Ælurus or Wah, of Nepal, is re-
placed by a larger and even stranger form, the Eluropus
of M. Milne-Edwards, a large bear-like mammal, quite
distinct from anything previously known. A long-haired
monkey inhabits the pine forests, remarkable for the
development of its nose, which the same naturalist has
proposed to name Rhinopithecus. The Takin of the
Mishnees of Upper Assam (Budorcas taxicolor) is repre-
sented by a second species of this most singular genus of
Ruminants. A new form of Cervidæ is remarkable for
its small horns and well-developed canines; and there are
a host of interesting novelties belonging to the insecti-
vorous and rodent orders in Père David's series. In birds,
M. Jules Verreaux, to whom the working out of this part
of M. David's collections has been assigned, has already
discriminated upwards of thirty new species. Amongst
these many belong to the remarkable genera discovered
by Mr. Hodgson in the hill-forests of Nepaul, and hitherto
unknown to occur elsewhere. Perhaps the most note-
worthy of them is a small Passerine form allied to Para-
doxornis, which has only three toes, a phenomenon
hitherto unknown in that typical order of birds... The
Reptiles and Batrachians obtained by Father David in
Moupin are also said to contain many novelties. Since
the lamented death of Prof. Duméril, their investigation
has, we believe, been undertaken by Prof. Blanchard, who
has within these few last days brought before the French!
Academy a notice of one of the most extraordinary ani-
mals of the latter group. This is no other than a gigantic
aquatic Salamander allied to, but distinct from, the now
well-known Sieboldia maxima, of Japan. The discovery
of this form of life in continental Asia is a fact of the
highest significance as regards geographical distribution,
as it was previously believed to be in the present epoch
confined to the Japanese Islands, though remains of a
closely allied animal (Andrias scheuchzeri) are found in
the tertiary freshwater deposits of Central Europe.

We have mentioned only a few of the principal discoveries of M. David, but enough has been said to show the importance of the additions he has made to zoological science, and to heighten the interest attaching to the complete investigation of the fauna of the Chinese frontier of Tibet, which this distinguished naturalist has thus inaugurated.

His

While Father David has been labouring among the snows of Central Asia, another not less arduous devotee of science has been risking his life in the tropical forests of Madagascar, and has likewise made many brilliant M. le Père Armand David is a missionary priest of the discoveries. M. Alfred Grandidier, who has now returned Order of Lazarists, who was for many years resident at from, we believe, his third voyage of discovery in that Pekin. Here he devoted much time and attention to the strange island, has shown that the riches and eccentricifauna of the surrounding country, which was at that period ties of its fauna have not yet been exhausted. little known, and entering into communication with the collections, which have only reached the Jardin des authorities of the Jardin des Plantes of Paris, supplied Plantes very recently, although brought to France before that establishment with many interesting novelties. the political storm of last autumn commenced, have not Amongst these one of the most remarkable was a new yet been fully examined. But they are said to contain deer with very peculiar horns and a long tail, which was very full series of several species of Lemuridæ, the comnamed by M. Alphonse Milne-Edwards Elaphurus davidi-parison of which is likely to lead to important results, anus, after its indefatigable discoverer. But about two besides examples of a new genus of Rodentia, and many years ago Father David moved the seat of his investiga- other Mammals of high interest. M. Grandidier has tions into still more promising quarters. It was, we also paid much attention to the fossil deposits of believe, the magnificent new species of Pheasants trans- Southern Madagascar, which contain the remains of the mitted by Bishop Chauveau from Ta-tsien-leou-a town extinct gigantic bird, pyornis maxima, and has arrived in Western Szechuen upon the frontiers of Tibet-that at some important results (such as the former presence first called his attention to the probable richness of this of Hippopotamus in Madagascar) which may ultimately district in other departments of zoology. Nor have his tend to modify some of the views generally held conexpectations been in any way disappointed. The collec- cerning the true nature of the fauna of this island and tions of Mammals, Birds, and Reptiles, obtained by Father its origin. P. L. S.

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FIG. 11.-Proportion 3: 4.-Cusped type. pairs, for comparison of relative motions, I found that the two upper joints alone were able to make good their title to independent periods of swing: the third joint acted merely as subsidiary to the second, merely serving to facilitate the bend at the second joint, and always synchronous with that bend, never able to establish a proper period of its own. All three joints conspired to allow undeviating vibration in a plane at right angles to that allowed by the topmost joint alone, just as though there

FIG. 12.-Proportion 3: 4.-Looped type. had been only two joints at right angles. I also tried three joints at angles of 90° and 30°, and two joints at an angle of 60°. They all gave similar results. It is clear that the planes of slow and quick vibration are determined solely by the position of the topmost joint, the former being that in which the pendulum can swing by the topmost joint alone, and the latter that in which the topmost joint takes no share at all, or the least possible share, at right angles to the first. However the joints may be

ranged, they conspire to establish a virtual second joint, right angles to the topmost joint, and at some point low it not necessarily coinciding with the position of ay one of the actual joints, and apparently varying for ifferent positions of the plane of vibration. At this stage I showed some of my pendulum's tracery > my brother-in-law, Mr. E. J. Routh, M.A., of St. eter's College, Cambridge, and received some hints from im which led me to adopt an arrangement whereby the osition of the lower joint could be varied, so as to bring he two periods of vibration into any simple proportion, s 1:2, 2:3, &c. This was done by a very simple mode of suspension,-two cords hanging from two fixed points Some distance apart, and passing through a small ring that could slide up and down the concurrent cords and be fixed at any height. In this arrangement I found the germs of an infinite variety of curious and elegant curves, that gave a new lease of life to my course of experiment. Before attempting anything, I drew in my pocket-book the skeletons of the curves that would be described corresponding to the proportions, 1:2, 2:3, 3:4, 4:5, 56, 6:7, 7:8, 8:9, in the periods of quick and slow vibration. Then I hung a bullet by two threads from two points about ten inches apart on the circumference of a child's wooden hoop, fixing the hoop upright with the bullet swinging inside the circle. Another bit of thread furnished the sliding-ring to nip the two convergent threads at any desired point, and a few trials enabled me to fix it pretty accurately for the proportion 1,2, so that the bullet would swing in the plane of the hoop in half the time it took to swing at right angles to the plane of the hoop, making two vibrations in the plane of the hoop to one vibration athwart. (The length of the pendulum varies as the square of the period of vibration, so the slider was at a point one quarter of the dis'ance from the bullet to the horizontal line between the two points of suspension.) It was with great interest that I watched the motion of my pensile bullet, and greeted the verification of my pocket book sketch. Pull the bullet aside and start it obliquely, and it describes a crescent-moon, the two horns being formed by the double swing in the plane of the hoop, while the length of the crescent measured from tip to tip is given by a single swing athwart the plane of the hoop. Start the bullet from rest at the centre by a sudden blow obliquely given, and it describes a figure of eight with its length athwart the plane of the hoop. (See Figs. 5 and 6.) Other proportions gave still more curious results in accordance with my skeleton sketches, and made me impatient to try them on a larger scale. The lead at my command I packed into a long-shaped zinc box, with a tubular orifice at the top, which in my service became the bottom. To the lead I added a stone jar containing some 10 lbs. of mercury, and made everything secure with cordage. The dependent tubular orifice seemed made on purpose to accommodate a few inches of wooden roller which carried the glass pen, and a diagonal beam in the ceiling of my bedroom offered a capital fixture for two rings about four feet apart, giving suspension to two iron chains by which my incongruous pendulum-bob was doomed to swing. To nip the chains together at the requisite height, I used a loose link which hooked into the corresponding links in the two convergents, and made a very rude and coarse adjustment, which left all accuracy to chance. It chanced, however, that the adjustment for the proportion 2:3 was beautifully accurate, and I shall never forget the feeling of delight which experienced while watching the marvellous fidelity with which the pen-point traced the curve appropriate to that proportion. The pendulum was drawn aside and started obliquely on one side of the plane of slow vibration, and having to make three vibrations across that plane to two vibrations to and fro, it compounds these into a curve like a capital Q with two tails, one on each side, looking like a swallow-tailed balloon. (See Fig. 9.)

At the end of the second to-and-fro vibration the pen returns to the point whence it started, except that friction compels it to fall short little by little at every stroke; but if the adjustment is accurate, as it was in this particular case, the shape of the curve remains the same from first to last, and the figure is filled up to the very centre by the orderly description of curve within curve conspiring to produce a web of lines of astonishing regularity. If the adjustment of the connecting link is very slightly inarcurate, the curve begins to change its shape little by little at every stroke, in one way or another, according as the link is too high or too low; and wonderfully intricate is the result, for after a due series of intermediate stages, the original figure reappears, but reversed; and after another series of changes it presents itself again to view in its original posture, but much diminished by the friction that has been in operation throughout all these changeful phases. It may be imagined how intricate the web becomes, though the limits of illustration do not allow me to give a specimen here. It was easy to eliminate all the transition-curves from the tracery, by depressing the paper for the proper interval, and allowing it to return to contact with the pen only at those distinctive phases when the original figure was reproduced either erect or reversed. I obtained a very curious specimen by applying this selective method to the case of the proportion 1 : 2, allowing the pen to mark only the crescents and the figures of 8 in alternate series, converging orderly to the centre. For the suspension of the paper, I fixed four pairs of upright rods at the four corners of a shallow tray, which could be slipped under the pendulum, and each rod gave support to an india-rubber band, which, with its fellow at right angles, was attached by a small hook to the corresponding angle of the paper. Each band could be slid up or down its rod, to allow of nice adjustment of the level of the paper, and the whole tray could be raised on a footstool or chair, to suit the elevation of the pendulum when the slider was run aloft in attaining the proportions nearer unity, such as 7: 8, or 8: 9.

The iron chain was soon exchanged for strong cords, passing through a narrow wire ring, which could be arrested at any point by a needle driven through both cords below the ring. This was a small improvement, allowing more accuracy in the adjustment of the slider, and therefore more accuracy in the proportion between the two periods of quick and slow vibration. But it was still very far from satisfactory. Meanwhile I had ordered a cylinder of lead, weighing half a cwt., to be cast, with a hole through the axis; for my zinc box full of "notions" was so tall that I could not bring the slider near enough to the centre of gravity to obtain any proportion lower than 1 : 3, and that only with great trouble. When the cylinder of lead appeared, I sawed it into two unequal portions, so that I could use either or both; and instead of simple cords, which twisted in a most troublesome manner below the sliding ring, I introduced a stiff rod of fir to carry the lead by a cross pin, and I used two pairs of cords passing through holes in a slider on either side of the central rod. This slider was a small block of wood pierced to fit the rod, and provided with a lateral screw to fix it at any required height. This arrangement ensured admirable steadiness and freedom from torsion, and a great many sheets were filled with the improved performances of the machine; but there still remained an important defect to remedy. The coarse cords, at the point where they entered the holes in the slider, made a very rough hinge for the cross vibration to rely upon, and it was manifest in the tell-tale records of the curves described that considerable change of period took place between the beginning and the end of the web; and the change was always such as to increase the disparity between the two periods, which could only mean that the level of the centre of quick vibration in the cords immediately above the slider was lowered when the range

of oscillation diminished. It was easy to see that a large oscillation would strain the cords to a greater height above the slider than would be called for in a smaller oscillation. The truth of this surmise was proved by the success of the remedy applied. Instead of cords I used two pairs of broad tapes, and instead of a solid slider I made one in two halves, embracing the rod in the centre and nipping the concurrent tapes on either side between their opposed faces, being clamped together by thumb-screws beyond the tapes on either side. Here the slider had no firm hold on the rod beyond the accuracy of its fit, which served to prevent torsion, but had firm hold on the pairs of tapes, pinching them with especial accuracy at the upper edge of the slit in which they lay between the two halves, and reducing the hinge there to a narrow line no thicker than the pairs of tapes instead of the gross thickness of the cords which they superseded. The improvement of the pendulum's performance on paper was very striking. When well adjusted, it was scarcely possible from beginning to end to detect any change in the shape of the figure described; scarcely possible, I say, for even now our hinge is not a mathematical line, and we do not obtain perfect mathematical accuracy in our results. Further improvement might be obtained by refinement in tapes and slider, or by increasing the total height of the pendulum, or by substituting some other form of hinge; but the form which I have described is so simple, and its performance so good, that I am content to accept its one very small fault for the sake of its many excellent qualities.

Figures 1-12 are the produce of this pendulum thus improved. They are only a few of the most interesting out of an endless variety of interesting curves, and are chosen as characteristic specimens of a series too extensive to be fairly represented except by a much larger number of illustrations. Figures 1 and 2 represent the proportion 13, the lowest that is easily attainable with out a loftier pendulum; and the following pairs of figures show successively the proportions 2:5, 1:2, 3:5, 2:33:4. Each of these is illustrated by two figures exhibiting the two chief types of the curve proper to that proportion. They may be termed the cusped type and the looped type. It will be seen that the two cusps in the first figure of each pair are opened into loops in the second, and that each loop in the first is doubled in the second. Between these two typical forms we have an infinite series of intermediate forms possessing features of great interest, those nearest the cusped type especially being characterised by a peculiar "watered" appearance, due to the intersection of two sets of lines very slightly inclined to one another. This is seen, for example, in Fig. 3, which errs a little from the perfect type.

Accuracy of proportion between the two periods of vibration could only be arrived at by repeated trials. The sliding-clamp sufficed for coarse adjustment, but for fine adjustment it was found necessary to attach a subsidiary weight below the large one in some way admitting of considerable range of position, so as to alter minutely the position of the centre of gravity. A heavy iron nut travelling easily on a screw-thread cut on the depending shaft that carried the pen supplied this want, and greatly facilitated the attainment of the utmost accuracy at command.

With a pendulum only seven or eight feet high, there is great difficulty in obtaining the curves that correspond to any proportions lower than 1 : 3, because the slider cannot be brought within a certain distance of the centre of gravity, which lies somewhere in the middle of the lead. To obtain the proportion 1: 3, that is, to make the pendulum swing three times across for every one swing to and fro, we must lower the slider within a foot of the centre of gravity (the length of the pendulum varying as the square of the period of oscillation), and to obtain the proportion : 4, the distance between the

slider and the centre of gravity must be 1-16th of Se height of the pendulum, or only six inches in the present instance; but three or four of those six inches are taken up with the thickness of the lead and the attachments of the tapes, and the rest with the depth of the slider, and so the curve cannot be obtained without a more lofty suspension for the pendulum. This greater elevation I found in the great octagonal room which Sir Christopher Wren built as the chief room of the Kujal Observatory in Greenwich Park. By means of two hooks fixed above opposite windows in this room, fra which my tapes converged to the middle, I got a height of eighteen feet, and was able to reach such pro portions as I :4, 15, 1:6. At this extreme it was realis amusing to watch the busy haste of the manifold crossvibration over-riding the staid gravity that marked the slower oscillation to and fro. To obtain proportions lower yet than these, I should want a great increase in heighte suspension; but there is no great inducement to attempt this, as the nature of the curve may be foreseen at a glance, and is marked by extreme simplicity-merely a zigzag o a string of beads.

Some of these experiments with lofty suspension w made on stormy days; and while watching the travels of the delicate pen-point, I could see that their regularay was slightly disturbed by every gust of unusual violence that beat against the high walls.

But this article would never end if I allowed myself to dwell on all the points that called for attention in the course of experiment which I have been describing. I fear I have exceeded due limits already, and feel that! owe an apology to the reader for so large a trespass on hi patience. My apology must be the elegance and exquisite symmetry of these natural curves in their admirable one dience to a purely natural law, and the great pleasure! have enjoyed-the sense of high privilege I have felt-in their investigation. I understand that these curves, af some of them, have been demonstrated before, by means of a stream of sand flowing from a hole in the base of a vessel that was used as the weight of the pendulum, and I believe that steel springs of elliptic or oblong crosssection have been made to trace such curves as that which first attracted my attention in the vibration of my slender acacia-twig; but I am not aware that any specim: as of the series have ever before been exhibited in a form that rendered them accessible to the public eye.

HUBERT AIRY

SOME SPECULATIONS ON THE AURORA

IN preparing a lecture on the Aurora Borealis some months ago, I was led to some speculations which may or may not be new, and may or may not be of some value I will submit them to the readers of NATURE.

I assume of course that the auroral rays extend to great heights above the surface of the earth, that they are sensibly parallel, and that their apparent point of con vergence is, generally speaking, that to which the freely 24, 1870, this point was close to n Pegasi at 8.30 P., CD suspended magnet points. In the great aurora of October inciding' very weli with the direction of the magnet Remembering that this aurora was witnessed over a large contemporaneous aurora in the southern hemisphere, and, part of the northern hemisphere, and that there was a assuming that at each place the direction of the auroral conceive the earth, during such an auroral display, as a streamers is approximately parallel to the magnet, we must globe with streamers of light radiating and diverging fran its polar regions, and spreading far out into space. The general direction of these streamers at different spots on paper and getting the magnetic curves with iron filings, the earth will be got by placing a magnet below a sheet of *To-night it is a few degrees below a Cygni (but not clearly defined t

JI P.M.

and then describing a circle, to represent a section through the axis of the earth so that the magnet shall occupy the central part, about two-thirds of its diameter. The portion of the magnetic curves outside the circle will cut the circle at different angles, and fairly represent the directions of the auroral streamers.

Now, Arago, in his catalogue of auroras, shows that during the months of September, October, March, and April we are especially favoured with auroras; and that in these months they are both brighter and more frequent than at other times. This periodicity indicates an extra terrestrial origin for auroras. Does it not show that during those months we pass through an auroral region, just as in November and August we pass through meteoric regions, or, in other words, that we intersect a ring of some substance capable of being electrified by the earth in its pissage, when there is any change in its magnetic power, and so rendered luminous? But it is impossible not to conjecture that this ring or disc is the very disc which is visible to us as the zodiacal light; for besides the fact of zodiacal light being specially visible during the same months, there is the positive evidence of spectrum analysis to the identity of the substances luminous in the aurora and the zodiacal light. We are led then to the hypothesis that there exists round the sun, and extending as far as our earth, an atmosphere, consisting of an unknown element, a gas of extreme lightness, and that this atmosphere is especially condensed in the form of a disc extending round the sun, but probably not concentric with it. The same element appears to exist in the solar corona, and was also detected in the vague phosphorescent luminosities of the sky on a particular evening, by, I think, Angström.

I wish to suggest, therefore, that catalogues of auroras may, like catalogues of meteors, determine auroral regions in the earth's orbit, and that two such regions are, in fact, already shown by Arago's catalogue, and that this periodicity, as well as the results of spectrum analysis, indicate a cosmical origin for auroras.

There is one more point which may be interesting. The luminous streamers have a lateral motion; they shift sideways, and in fact rotate round their pole. Is this motion of rotation always, or even generally, in the same direction? I have not observed it often enough to speak with confidence. But if so, it must have some definite cause, and will be analogous to that of rotation in a definité direction of an electrical current round the pole of a magnet. The earth must be looked upon as a delicate solar electroscope and magnetometer, and the electrical discharge round the earth is stratified, and is in lines and strata that have, perhaps, motions in definite directions.

It may be worth remarking that the 22nd, 23rd, 24th, and 25th of October are the most famous days in the year for auroras, at least in the present century, and that the greatest displays of all on those days have happened at intervals of multiples of eleven years. Last year we had splendid auroras on the 24th and 25th; there is, therefore, some ground for expecting fine auroras on the same nights this year, if the auroral cycle corresponds to the sunspot and magnetic cycles. J. M. WILSON

NOTES

We learn from Indianapolis journals, received at the moment of going to press, that the American Association for the Advancement of Science commenced its sittings on the evening of August 21 by an opening address from the retiring president, Prof. T. Sterry Hunt, on the Iron Interests of Indiana, in which he completely sustained every claim that had been made for the State, showing conclusively that it has the elements within its borders from which to secure a manufacturing future that shall make Indiana the mediterranean workshop for the whole country. The sections commenced their sittings on the following day, and San Francisco was fixed en as the next place of meeting. An extra

double number of the American Naturalist for September 15 will give a full report of both the opening address and the sectional proceedings. In a future number we shall give an epitome of all matters of interest discussed at the meeting.

M. JANSSEN has been commissioned by the French Government to proceed to the East to observe the total Solar Eclipse of December next. He has, therefore, been compelled to decline the offer made to him by the British Association to take part in the British Expedition.

THE President of the Royal Society has received a telegram from the Government Astronomer, Melbourne, that the Eclipse Expedition will leave that port on November 20.

WE regret that owing to the omission of a sentence, the note respecting the distinguished visitors at Section A of the late meeting of the British Association, read incorrectly in a small We now supply proportion of the edition of our last number. the omission by giving the following probably unexampled list of Senior and Second Wranglers and Smiths' Prizemen who were present:-Adams, Cayley, Challis, Stokes, IIon. J. W. Strutt, Hopkinson, Kelland, Tait, Wilson, Thomson, Maxwell, Sylvester, Clifford, Jack, J. W. L. Glaisher; of these the first nine were Senior Wranglers.

WE learn from the British Medical Journal that in accordance with the will of the late Dr. Lacaze a prize of 10,000fr. is to be awarded by the Faculty of Medicine of Paris every second year to the best work on phthisis and on typhoid fever alternately. The first prize will be awarded at the end of the academical year 1871-2, for the best work on phthisis. Essays (with a distinguishing motto and the author's name in a sealed envelope) must be sent in before July 1, 1872. The prize is open to foreigners.

IN a paper read before the Natural History Society of Boston (U.S.), Mr. W. T. Brigham gives an account of several remarkable earthquakes that have occurred in New England, with a list of all such phenomena that have occurred in that region from 1638 to 1870. Some of these disturbances appear to have been violent and protracted.

WE understand from the Geological Magazine that there will shortly be published a Geological Atlas of England, by Mr. W. Stephen Mitchell. The Atlas will contain the following Maps :1. Cambrian (of Survey); Lower Cambrian (of Sedgwick). 2. Lower Silurian (of Survey); Middle and Upper Cambrian (of Sedgwick). 3. Upper Silurian (of Survey); Silurian (of Sedgwick). 4. Old Red Sandstone; Devonian. 5. Carboniferous Limestone; Yoredale Beds. 6. Millstone Grit; Coal

IO.

Measures. 7. Permian (of Survey); Pontefract Group (of Sedgwick). 8. New Red Sandstone; Rhætic (Penarth). 9. Lias. Lower Oolite. 11. Middle Oolite. 12. Upper Oolite. 13. Wealden; Neocomian. 14. Gault; Upper Greensand ; Chalk and Chalk Marl. 15. Eocene. 16. Crag. 17. Alluvium. 18. Bone Caves. 19. Metamorphic (?) 20. Igneous. The Maps will be printed in colours, each Map exhibiting only the range of one formation, and the names of places on the formation. In some few cases, where it is requisite, as a clue to the locality, to introduce the names of places near, but not on, the formation, these will be printed in a different type. The Maps (11in. by 9 in.) are based on a photographic reduction of the last edition of the Greenough Map, which is published under the direction of a committee appointed by the Geological Society. In all cases where, through researches more recent than this last edition, any changes have been adopted in the grouping of the beds, this atlas conforms with the latest alterations. The revision of the proofs of particular maps has been kindly promised by Mr. W. Boyd Dawkins, F. R.S., Mr. W. Whitaker, Mr. H. Bauerman, Mr. J. W. Judd, Mr. Charles Moore, Mr. W. T. Aveline, and others. Letter-press will accompany each map, giving in a tabulated form the subdivisions of the formations, the

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