not directly comparable: that the mercury in GayLussac's tube is hot, while a barometer is generally cool? A student of Nature will scarcely be taught much that is satisfactory concerning Gay-Lussac's beautiful method of determining vapour densities, by being led away at once into intricate formulæ "which burden the memory, without cultivating the understanding." This one example will sufficiently indicate the fault which runs through the whole volume before us. Much new and valuable matter, albeit besprinkled with formulæ, has been added by the translator; and various passages in the original have been modified or otherwise corrected. But, though we have no hesitation in saying that the original has been thereby improved, yet the final result is neither remarkable for its novelty, nor edifying from its simplicity.

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his Correspondents. No notice is taken of anonymous communications.]

Thickness of the Earth's Crust

I TAKE in NATURE in parts. Your part for May last has just reached me in Calcutta, and is somewhat rich on the question of the thickness of the earth's crust; for three of its four numbers contain letters on that subject. First, my letter to you, p. 28; two critiques upon it from "A. J. M." and Mr. Green, p. 45; and a third from Mr. David Forbes, p. 65.

Reply to "A. J. M." I do not think it safe to draw inferences from a comparison the members of which differ so materially; a plate of lamp oil, probably a quarter of an inch deep, and the solid crust of the earth resting on a fluid mass 3,856 miles deep, supposing the crust, according to the thin-crust theory, to be 100 miles thick. To be sure, the motion in the experiment is very much greater than precession; but the depth of fluid is also very different, and the cases are not parallel. Moreover, in the one case, the oil rests on the plate, weighed down by gravity, and is easily carried round bodily with the plate. This is different to the hard crust rubbing over a depth of fluid. I see the writer, like M. Delaunay, relies much on the extreme slowness of the motion. More on this soon. We shall have to beware how we adopt the phrase "a rope of sand," for if we use the rope slowly enough, it may become in our hands a "rod of iron."

Reply to Mr. Green. By "pushes" I did not mean mechanical knocks, but merely geometrical movements. The pole of the earth goes round the pole of the ecliptic in a circle in about 26,000 years. I divided this circle into a multitude of little pieces. Nor was my description meant to represent this motion as being by fits and starts, but only in portions, to assist the mind in a popular explanation, not of precession, but of the thing I wanted to be understood, the slipping of the hard crust over the fluid. I think it is very likely my own fault that my description has been misunderstood.

Reply to Mr. David Forbes. Mr. David Forbes glides out of the discussion on the plea, that after all I make out that Mr. Hopkins' calculations were based only on "an idea.” But so is M. Delaunay's opinion based on an idea. an idea.

We must start with

Ideas are of two kinds, sound and unsound; and if the idea we rest upon is sound, we cannot possibly do better than build upon it. M. Delaunay thinks his idea is supported by an experiment. I have tried to find a description of the experiment, but without success. I altogether doubt whether any experiment with models can be devised to lead to trustworthy results, regarding such a huge mass as the earth affected by such slight motions as precession. Mr. David Forbes says he went to the Royal Society to hear a paper of mine read on the constitution of the solid crust of the earth. It was natural that he should suppose from the title, that it might bear upon this question of the thickness of the crust. But this is not the case at all, as he would find. M. Delaunay's strictures on Mr. Hopkins' investigation seemed to me so important, that I did drag in, I may say, an allusion to them in a note. It is very likely that, as my paper was almost entirely a calculation of mathematical formulæ and their numerical application to the pendulum observations lately made in India, the paper itself was not read aloud, and that conversation turned on the incidental note.

I propose now to view the subject in a new light, an begin de novo; and I feel confident that your readers that there is more to be said for Mr. Hopkins' method th have by this time been led to think.

because the precessional force is extremely small. The precessional motion is no doubt extremely slow: But the : ticles of the earth's mass have a good deal more to də z matter than to partake of this small motion. Every twestr hours they have to undergo a strain, first this way and the such that I believe no fluid, however viscous, could Though the precessional force is so minute, it is the resal residuum of an almost infinite number of other disturbing nearly balanced; as I proceed to show.

Let G be any point in the earth's mass; its distance the centre; a the radius of the earth; the distance of t the angle between 6 and ; S the sun's mass. Then, cos ing the sun's action by itself, its attraction on GI res parallel and at right angles to c, and from the former po subtract the sun's attraction on the disturbing forces on G are wanted. These are, neglecting the smallest quantities. 456 S& cose and sine. 13

For the sake of a name I will call the plane through the centre, at right angles to the line joining it and the sun.. Boundary Plane, as it intersects the surface almost exactly = boundary line between sunlight and darkness. It will be olsam that at this plane the first of these disturbing forces equais and is positive on the sun side of the plane, and negative sam opposite side. The amount of this force is the same at all lying in any plane parallel to the boundary plane, and the gate of the positive forces on the one side, and of the negat the other, would be in each case a force acting through earth's and sun's centres, but for the slight deviation of ta earth's figure from a sphere, and the consequent arrangemer its mass. Suppose, for argument's sake, that the particles of 2 earth's mass are held invariably together as a rigid body, the the disturbing forces parallel toe will amount to an aggrega positive force, and an aggregate negative force, tending separate the two parts of the earth formed by the boundary pime. These forces are equal to each other, and pass nearly through the earth's centre, at opposite and equal distances from They form, in fact, a mechanical "couple," and twist the earth round some diameter lying in the boundary plane. The arm of this couple is a minute quantity depending upon the ellipticity of the earth's figure. Hence the movement of the couple, from w precession and nutation arises, is a minute quantity, while the force of the couple (which is the tension of the earth's mas pe pendicular to the boundary plane) is not of that minuteness. Th other disturbing forces, represented by the second formula, tend towards c, and compress the mass. They would all balance each other, were the earth spherical. The resultant of the forces on the sun side will be a minute quantity of the order u the ellipticity, and will act at a certain distance from the centre: and the resultant on the opposite side will be an equal force, ing at an equal distance from the centre, but in an opposite d rection; so that again there will be a couple of minute powe assisting with the other couple to produce the combined motica of precession and nutation. In this case, although the forces nearly balance each other on cach side the boundary plant, parallel to it, and but a small resultant follows, yet the particles of the mass have to undergo the compression from opposite sides, as in the other case they have to sustain the tension caused by the opposing forces tending to separate the two halves of the earth.

The moon will produce forces precisely similar to these, and a little more than twice their amount. The forces of the sun and moon do not come to their maxima and minima at the same time, except at new and full moon. At other times they partly con spire or counteract each other according to their position. Sun and moon together will produce most irregular cross-strains through the mass, if the particles are held together by any degree of rigidity.

It will be seen, then, that as within twenty-four hours every particle of the mass in its rotation is carried through the boundary plane some days in the year, and most of the particles every day, every part of the mass will be periodically subject to the maximum strain I have described as taking place at that strain, and most parts twice a day, as well as the compressing force at right angles to c.

The same will be the case, and at different times, except at new

'oon and full moon, at the boundary plane appertaining to the oon. The result is that all parts of the mass are perpetually ndergoing considerable cross-strains, for the forces of tension nd compression will not relieve each other, as they act at right ngles to one another.

If the mass of the earth were not rigid, but sufficiently Elastic, like, for instance, a globe of india-rubber, the particles would yield to their small disturbing forces; and the result would e that each particle, as it arrived by rotation at each point of its ircuit, would move in proportion to the force acting on it, one vay or the other. In this case there would be nothing to cause he axis to move; the earth would steadily revolve, and no precession or nutation would occur. The whole mass would, as it were, breathe, heaving its surface and drawing it in again in a complicated undulation.

But observation shows that the earth has precession and Dntation; and therefore the mass cannot be thus elastic.

If it be only partially rigid, then there would be a corresponding degree of yielding; but precession and nutation would still be produced, and a strain, in a somewhat diminished degree, affect the mass

Now, mathematical calculation made on the hypothesis of the earth's mass being absolutely rigid, and that throughout, shows that the annual precession would be 51.3566".* Astronomical observation shows that the precession is actually 50'1". The remarkable nearness of these results is sufficient proof that the earth's mass is not the limp thing some take it to be; all viscous-fluid from only 100 miles down to the centre, moving so slowly, that it gives inertia to the hard crust (supposed thin) as if it were all solid! It is more like the highly rigid mass which Sir William Thomson has shown it to be from other considerations. JOHN H. PRATT

Calcutta, July 15

Meteorology in South Australia

As it may be interesting to some of your English readers to hear something of natural phenomena in such an out-of-the-way part of the world as South Australia, I forward a description of three very fine meteors which have lately been seen here, as well as a splendid display of Aurora Australis.

On January 5th, 1871, at about half-past nine P.M., I observed a splendid meteor. It appeared at first like a fixed star about three times as large as Jupiter, or say six or seven inches in diameter, and was probably about 15° above the horizon, or nearly of the same apparent height as a large star which was just below the planet Jupiter, a little to the west of him and within half an hour of the meridian. The meteor, which was very brilliant, somewhat of the appearance of Jupiter, remained apparently stationary for, at least, five seconds; it then gradually began to move from a due north position to a direction about S. S. E., and in a horizontal line; it then burst into several smaller meteors and went out, having lasted fully twenty seconds altogether. The moon was shining brightly at the time, being a few days off the full.

On the same night, and at about the same hour, a large meteor was seen by a survey party at Hookina, a place about 400 miles north of Adelaide. The surveyor in charge of the party (Mr. Hamilton) from whom I obtained the particulars of this meteor, says he was facing the east when he observed going from N. E. to S. E., describing a large arc at an apparent elevation of 20°. He describes its colour as greenish, and so bright that it almost overpowered the light of the moon. It ultimately burst with a loud explosion into a number of fragments of red and blue colours, and the earth was felt to tremble as though a shock of an earthquake had occurred.

On the 25th March last, at about twenty minutes to three o'clock in the afternoon, I observed a meteor in the full blaze of the sun.

The

It appeared like a bright brass-coloured ball of fire, shooting through the sky like a rocket; it seemed to have a green and blue light round a central brass-coloured nucleus. meteor appeared about three inches in diameter; it had a whitish comet-like tail, about three feet long, and it came from the N.N.E. and travelled downwards towards the S. S. W., so that as I was looking south it appeared to come over my left shoulder. It lasted about ten seconds, then burs: without noise, and became dissipated. This meteor seemed to fall at about 15° from the horizon.

In the S. A. "Register," a few days after seeing the last ⚫ See this worked out in my "Mechanical Philosophy," 1st edit. p. 562, 2nd edit. p. 540.

described meteor, it was stated that a surprising sound was heard at Point Macleay, and other places about fifty or sixty miles to the south-east of Adelaide as of the firing of cannon, and the correspondent of that paper at Mannum (a place on the River Murray, about sixty miles east of Adelaide) writes as follows :— "On Saturday last (25th March) at exactly 2.45 P. M., I was looking down the Murray River, when suddenly my attention was attracted by a large ball of fire falling from the heavens in almost a perpendicular course. The lakes are from here in the direction which it indicated-almost due south-so that I have no doubt the extraordinary phenomenon mentioned as having occurred on the shores of Lake Alexandrina, may have arisen from one of the causes assigned, viz., a falling meteor or an aerolite. What I saw was evidently the explosion immediately preceding the fall, and it presented the appearance of a luminous meteor."

The display of "aurora australis" which I observed on the 23rd March last, commenced at about eight o'clock P. M. It increased in brightness till eleven o'clock, when it gradually faded away. At about two o'clock A M., while at a ball, I came out on the balcony and observed the whole southern sky lighted up by a most gorgeous display of aurora. It occupied about 70° or 80° of the horizon, extending from about S.S.E to S. W., and reached to a height of say 60° above the horizon. It was of a splendid red rose colour and streaked with beams of white light at various distances apart-say two bands of white in every 10°. These white bands appeared about two feet to five feet wide, which would answer to say 5° observed by the eye alone. The display was so bright that by placing my hand with the fingers apart at about two feet from a lady's white dress, I could distinctly see the shadow of each finger. This aurora was also seen in Victoria and New South Wales.

I may mention that Adelaide is situated in south latitude about 35°, and longitude 138° 40' M. M. FINNISS Adelaide, June 19

I agree entirely in this view except as to what would seem to be implied by the expression in spite of. I fail to see any inconsistency between the idea of a substance "thinning out and a permanent solar aurora,

What I intended in adopting and endorsing this auroral hypothesis was simply this: to express the belief (which I still hold, though with no great tenacity) that the substance which composes this green-line layer is also found in the upper regions of our atmosphere in a state of almost inconceivable tenuity, and at an elevation of certainly more than one hundred miles; and, further, that the peculiar filamentary and radiant structure of the corona, and very possibly its luminosity to some extent, are due to solar forces closely analogous to those which produce our terrestrial auroras.

Or in other words, that an observer, at the planet Mars for instance, looking at the earth during a period of auroral activity would see its poles capped by a corona in substance, structure, and to some extent in origin, closely analogous to that which is permanent around the sun.

And if we grant the identity of the 1474 line with that which is, to say the least, so closely coincident with it in the auroral spectrum, it is difficult to see why the hypothesis should be considered "extraordinary," or per se improbable.

That the enormous chemical, thermal, luminous, and magnetic activity of the solar surface should be unaccompanied by manifestations of what we call electric energy seems far more unlikely than the contrary; and if such energy operates we should naturally look for phenomena, the counterparts of those by which it shows itself here, but on the solar scale of course.

As to the identity of these lines, however, there may fairly remain some doubt. This line in the spectrum of the aurora is so rarely seen, so faint, and so difficult of observation, that, although the few observations thus far obtained show even a surprising agreement with each other and with this idea, it is safer to maintain a cautious reserve.

Dartmouth College, U.S.A., August 16

C. A. YOUNG

Lecture Experiments on Colour

FOR some time I have been taking an active interest in the phenomena of colour, and have read with much pleasure the papers of Mr. Strutt and other gentlemen, and the abstract of the interesting lecture recently delivered at the Royal Institution by Prof. Maxwell. I have repeated many of the experiments of these observers, and have successfully exhibited them in public in a modified form, and in a way which can be readily repeated by other lecturers without the aid of the elaborate contrivance used by Prof. Maxwell. The following experiments make no pretension to rigid accuracy, but are merely described as striking lecture-table demonstrations of well-ascertained but little known scientific facts. I use the lime light for their exhibition, as it suits my convenience better than the electric light, though many lecturers prefer the latter.

A beam of light from the lantern is passed through a slit, focussed by a lens, refracted by a disulphide of carbon prism, and the spectrum exhibited in the usual way. A flat cell containing a solution of potassium permanganate is next placed in front of the slit. With a weak solution and narrow slit a series of black bands are produced in the green part of the spectrum, but with a stronger solution the green and yellow are completely cut out, allowing only the red and deep blue lights to pass. widening the slit these bands of coloured light of course increase in width also, gradually approaching each other until they overlap, producing a fine purple by their admixture.

On

If the experiment be repeated, substituting for the permanganate an alkaline mixture of litmus and potassium chromate in certain proportions, only the red and green light are transmitted, the blue, and especially the yellow, being completely absorbed. On widening the slit as before, the red and green bands overlap, and produce by their union a very fine compound yellow, while the constituent red and green are still visible on each side. The effect is most striking when by the widening of the slit a round hole is exposed in its place, when there appear on the screen two circles, respectively green and red, producing bright yellow by their admixture. This experiment is the more striking as it immediately follows the process of absorbing the simple yellow. The mixture above described (suggested by Mr. Strutt) answers better than a solution of chromic chloride.

Of course, it is a well-known fact that all natural yellows give a spectrum of red, yellow, and green, and a common effect illustrating the compound nature of yellow is noticed when exhibiting a continuous spectrum on a screen. When the slit is narrow the green is very fully developed, and only separated from the red by a very narrow strip of yellow, while on gradually increasing the width of the slit the red and green are seen to overlap, producing the brilliant yellow we generally notice. the purer the spectrum the less yellow is observed.

Thus

If the continuous spectrum be produced with a quartz prism, a little management and adjustment of the distance of the screen will cause the two spectra to overlap, so that the red of one may be made to coincide with the green, blue, or any desired tint of the other. The same result is obtained by employing two slits at the same time, the distance between which can be adjusted. By this means two spectra are obtained simultaneously, any portions of which can be made to coincide.

I have not tried to use a double refracting Nicol's prism, as is suggested by Mr. Strutt in the number of NATURE for June 22, A saturated solution of potassium chromate absorbs all rays more refrangible than the green, while a solution of ammonio. sulphate of copper stops all but the blue and green. These statements may be proved by placing flat cells containing the liquids in front of the slit of the lantern, and on placing one cell in front of the other in the same position the green light only is transmitted. This experiment serves to explain the reason that the mixture of yellow and blue generally results in green, all other rays being absorbed by one or other of the constituents.

By placing the two cells in front of separate lanterns, and throwing discs of light on the screen, a beautifully pure white is produced where the blue and yellow overlap.

I employ one lantern only for this experiment, using two focussing lenses side by side to produce the overlapping circles of light.

I also employ a cell with three compartments, containing solutions of aniline red, ammonio-sulphate of copper, and a mixture of potassium chromate with the last solution, and projecting images on the screen by means of three lenses fitted on the same stand but capable of separate adjustment. I can thus exhibit overlapping circles of brilliant red, blue, and green light, which

Mr. Stone and Prof. Newcomb

I AM Sorry, indeed, that anything in my answer to Prof. Newcomb should be unsatisfactory to Mr. Stone. It will certainly be hard if after drawing upon myself Prof. Newcomo's indqua tion by advocating Mr. Stone's claims, I should find that I have unwittingly offended Mr. Stone also.

It is the misfortune of a writer on science that he has often to deal with overlapping claims; and when he adheres unflinch ingly (as I have always done) to what he regards as the strict line of truth, he cuts off a little from the claims on either side, and so offends both claimants. I have found myself in the same difficulty as respects the work of Dr. De la Rue and Fr. Setchy in 1860, and I fear the result may have been the same in that case also.

In another case, that of Mr. Lockyer and his fellow-workers in spectroscopic solar researches, I freely admit that what I re garded as the line of truth when I wrote "Tae Sun," I now no longer regard as strictly such, evidence having been produce! which has satisfied me to that effect. Even in this case, however, I have in the first place very little to correct, and in the second I am by no means certain that I shall be able to satisfy all or any of those concerned.

Fortunately or unfortunately, the writer who cannot please all proves equally his desire to do justice to all by leaving al d satisfied. This is commonly the fate of the true neutral. I must confess, however, that I cannot see what reason Mr. Stone has for being dissatisfied, since I have ascribed to him, much to Prof. Newcomb's dissatisfaction, the final and complete solution of a problem which both have dealt with very ably. I am still waiting to hear the nature of Prof. Newcomb's objections. Whatever they may be, I am assured of this that in defending (if I can defend) my own work, I shall be advocating Mr. Stone's claims. I hope that in so doing I shall not very grievously offend that gentleman, towards whom I eatertain the most friendly feelings RICHARD. A. PROCTOR

66

Saturn's Rings

THE reviewer of Lieut. Davies's work on Meteors has somewhat misunderstood the extent to which I have been indebted (in preparing my treatise on Saturn) to Prof. Maxwell's excellent Essay on the Saturnian Ring-System." I have quoted in all two and a half lines from that essay, with proper reference to it, and I have devoted one-third of a page to summarising the mos, un portant section of the essay. All the rest of my chapter on the Nature of the Rings was written before I had seen Prof. Max well's contribution to the meteoric theory of the ring-system. I may add that every result in Saturn, which is not districtly referred to authority, or else obviously common property, bas been worked out by myself, as my note-books will abunday testify. RICHARD A. PROCTUR

Brighton, August 28

A Rare Phenomenon

SUNDAY, the 13th August, and several days before, baving been very hot and dry, a great deal of dust was suspended in the atmo sphere, which caused without doubt the intense red colour of the setting sun, and might contribute to the phenomenon I am about to describe. This phenomenon may easily be understood by means of a globe bisected by a meridian plane, one half of if representing the celestial vault. Beginning at the eastern end of the equator, the space between the 40th and 50th degree of longitude may be tinged with reddish grey; then the space be tween the 60th and 75th degree, further, that between the

5th and 105th, and finally that between the 115th and 140th egrees. But the intensity of colour must vary inversely to the readth of the stripes, and the three stripes left between the red nes be filled with a pretty vivid blue. This hemisphere placed upon a table with its southern pole pointing towards unset will afford a tolerable portrait of the aspect of the sky as t appeared immediately after sunset, and continued unchanged or more than a quarter of an hour. The stripes were not visible near the horizon, but were very distinct at an altitude of about fifteen degrees, and almost disappeared about the zenith. No cloud was seen during the occurrence of the phenomenon.

These stripes were certainly parallel in reality, and their apparent divergence may be accounted for by perspective. The reddish stripes may owe their colour to sunlight reflected back from the particles scattered in the atmosphere. But why did the celestial vault show so distinct a blue colour in the intervening bands? Yet, probably, this phenomenon is more easily to be explained than the infinite variation of evening colourings that want a valid explanation to this day. Magdeburg, August 19

THE AURORA

A. SPRUNG

silvery white, without a trace of that rose colour which characterised the three great displays of last autumn, The main portion of the light was in the north-western quarter of the heavens, and it was sufficiently strong to see large print by. Extending from the north-west and reaching the north-eastern horizon arose three luminous arches concentric with each other, the 1st about 150 altitude, the 2nd about 25° altitude, and the 3rd about 40° altitude. These were connected by radial tongues of light which were ever changing their height. There was another marked and isolated nucleus about and around a Lyræ.

At about 10.45 P.M. there were most curious rays shot up from the arches in the north, and concentric with them These shooting arches, if I may call them so, had at the horizon an apparent angle of about 150° to 180°, but as they approached the nucleus in Lyra, they contracted and lost themselves in sheets of white light. On applying the spectroscope I found one bright line visible all over the heavens excepting on the south horizon for an altitude of about 25°. The spectrum obtained on the north-west gave five bright lines, of which I send a drawing.

hydrogen. The instrument I used was one of Browning's direct vision spectroscopes-an instrument that gives the best results with the minimum amount of light. Of the bright lines, two were strong, one was medium, two were very faint. In the accompanying map I have put the solar spectrum at the top and carried the chief lines down for comparison. In putting numbers to the lines have been directed by their degrees of intensity.

No. I is a sharp, well-formed line, visible with a very

narrow slit.

FRUIT CLASSIFICATION*

No. 2. A line very slightly more refrangible than F. The side towards D is sharp and well-defined, while on the other side it is nebulous.

No. 3. Slightly less refrangible than G, is a broad illdefined band only seen with a wide slit.

No. 4. A line near E, woolly at the edges, but rather sharp in the centre. This should be at or near the position of the line 1474 of the solar corona,

No. 5. A faint band coincident with 6, extending equally on both sides of it.

The barometer stood at 29'574 in.; the thermometer at 613. A gentle wind was blowing from the south-west, and the sky was free from clouds. Observatory, Dun Echt, Aberdeen

LINDSAY

The classification which Dr. Dickson suggests for the consideration of botanists approaches most nearly to that indicated by Schacht in his "Grundriss," of which, indeed, it may be viewed as a modification and expansion. Schacht grouped fruits the seeds to escape; (2) splitting fruits or Schizocarps, which under three heads- (1) Capsular fruits which dehisce to allow

*"Suggestions on Fruit Classification." By Alex. Dickson, M.D.; Regius Professor of Botany in the University of Glasgow. Read before the British Association, 1871.

break into pieces which do not allow the escape of the seeds; and (3) fruits which neither dehisce nor fall into indehiscent pieces, including Berries, Drupes, and Achenes. As this last group is very heterogeneous, Dr. Dickson prefers to consider Berries, Drupes, and Achenes severally, as forms of equal value with Capsules or Schizocarps, and therefore would divide fruits into five groups, viz., 66 Capsules," "Schizocarps," "Achenes," 'Berries," and "Drupes," as will be seen in the following table :

10. Acheve (in restricted sense.--Pericarp not adherent to seed: eg.. Ranunculus, Rumex, Ulmus, Fraxinus, &c.

1. Caryopsis.-Pericarp adhering to seed: e.g., Gramineæ, &c. 12. Cypsela.-Pericarp not much indurated: e.g., Compositæ, Valerianacea, &c.

13. Glans.-Pericarp hard: e.g., Quercus, Castanea, Fagus, Corylus, &c.

14. Uva-Superior: c.g., Vitis, Sola num, &c.

15. Bacca (in restricted sense).-Inferior: e.g., Ribes, Vaccinium, &c.

(Prob- 20. (Name wanted) Superior: e.g, sistence-fleshy, included ably the twoforms Ilex, Empetrum. leathery, or fi- this head should 21.

brous. As a rule, indehiscent.

under

be embraced by a

single term.)

Pome.-Inferior: e.g, Pyrus, Cratægus, Sambucus, &c.

plant is disseminated, probably the most philosophical method of classifying fruits would be according to the nature of the parts disseminated. To carry out this principle rigorously, however, would lead to practical difficulties, far outweighing any advantag gained. Atthe same time, it is evident that the foregoing classfication satisfies, in a general way, the conditions of such 2 method; thus, in capsules and berries, the seeds, as a rule, are the ultimate parts disseminated; in Drupes, the stones; in Schizocarps, the mericarps or joints; and in Achenes, the fruits an wholes. As refractory exceptions, however, may be mentioned, those cases where the seed minus its testa is the part ultimately disseminated, for example, in Oxalis, where, on dehiscence of the capsule, the elastic testa becomes ruptured, violently expelling the body of the seed with the tegmen; or in the so-called dru paceous seeds (c.g. in Punica) which are doubtless devoured by birds, and, after digestion of the pulpy testa, the body of the seed with the hard tegmen is evacuated, and dissemination Or, again, in such a drupe as the apple, where the induration of the endocarp is slight, we have the fruit behaving as a berry, and dissemination taking place by means of the seeds.

occurs.

Some botanists may perhaps be surprised to note the omission of the terms siliqua and silicula, so universally employed to desig nate the fruits of crucifera. A little reflection, however, is sufficient to make it evident that, if distinctions so trifling in character, as those which separate these fruits from other valvular capsules were consistently carried out in practice, the terminology woul become altogether intolerable. A similar argument may be adduced in favour of the suggestion made in the foregoing table, as to the propriety of devising some common term which wil supersede those of follicle and legume.

NOTES

WE are happy to say that the Eclipse Committee has bea perfectly successful in its attempt to send a complete set of instruments to Australia; and a code of instructions is being drawn up in order to ensure similar observations being made at all stations.

It is now announced that the Swedish Government has atandoned the intention of establishing a colony in Spitzbergen for permanent scientific observation, mainly, it appears, in conse quence of jealousies on the part of the Russian Government.

THE autumn meetings of the Iron and Steel Institute were commenced at Dudley on Tuesday morning, under the presidency of Mr. Henry Bessemer. About 250 members of the Institute were present, and during the course of the proceedings, the secretary announced that forty-seven new members had been elected, amongst whom were the Earl of Dudley, and Sir Antonio Brady, of London. The President, in opening the meeting, described the locality in which it was a sembled as one of the most interesting districts this country presented to the iron manufacturers—a district, indeed, in which they might say that the great iron industry took its rise; its very cradle and birthplace. Mr. H. Johnson, mining engineer, read a paper "On the Geological Features of the South Staffordshire Coalfield, in Special Reference to the Future Development of its Mineral Resources." The South Staffordshire coalfield, one of the oldest in Great Britain, he said, was remarkably rich in coal, ironstone, and limestone. The secretary then read a paper by Mr. John Giers, Middlesboro', "On the Ayresome Inaworks, Middlesboro', with Remarks upon the Alteration in the Size of Cleveland Furnaces during the last Ten Years." A paper was read by Mr. Thomas Whitwell, Thornaby Ironworks, Stockton, "On further Results from the Use of Hot Blast Fire, brick Stoves." Mr. T. W. Plum, Shifnal, Salop, read a papr "On the Advantages of increased Height of the Blast Furnaces in the Midland District." The last paper was read by Mr. J. Lowthian Bell, New castle, "On Mr. Ferries' Self-coking Fur A large party then proceeded by train to Tipton, where the ironworks between that town and Wolverhampton were visited, and a pleasant afternoon was spent in investigating the

nace."