a recent number of the periodical, of which he is a joint Henle, in his work on Anatomy, has made the observation that people have very vague ideas about objects even which are assumed to be well known; e.g. the query is often put, How many feet has a crab? or, How many toes has a cat?-questions which receive most varying answers ever in well-informed and educated circles. If, then, the question be put in the company of half a dozen people, which finger is the longest-the index ring" (fourth) finger?-the query can (fore finger) or the " but seldom be answered before the members in question have been looked at. It seems, further, very probable that the authors of well-known anatomical works have laid down as being the rule that which they have observed on their own hands, so that we are enabled to tell in what respect, as to digital arrangement, such and such savant is endowed. For instance-Weber says that the "ring" finger is only slightly shorter than the index; Carus holds that the latter digit is shorter than the ring finger; Henle is of the same opinion; while, according to Hyrtl, it is the index which comes next to the middle finger (the longest) in length; and Langer, lastly, says that the index finger, but that there is generally shorter than the "ring are individuals in whom they are nearly of the same length. Have these variations a morphological significance or not? For the solution of this, answers to the following questions are necessary : (a) How are the animals which come next after man, in other words, the apes, and especially the anthropomorphous apes,† off in this particular? (3) What is the case with the lower races of mankind in the same particular? (7) What is the most usual digital arrangement in this respect among the European races of man? and lastly, (8) Which proportion of the two digits in question has been accepted as the most beautiful and symmetrical, and either knowingly or unknowingly adopted in art? 66 1. With regard to the Ape, the index is-and often ring" finger. The difconsiderably-shorter than the ference in length is much more considerable in the Chimpanzee than in the Gorilla; the greatest difference, that of 20 mm., having been found in the cast of a hand of a male Chimpanzee. 2. Drawings-made by placing the hand upon paper, the axis of the middle digit coinciding with a straight line at right angles to the front or hind margin of the paper, supposing the latter to be a parallelogram, and then following the outline of the fingers with a pencilwere made of twenty-five male and twenty-four female negroes, with the following result : (a) Among the males twenty-four had the "ring" finger longest, the average difference being 8 mm., while in the remaining instance both fingers were of the same length. (b) Out of the females the "ring" finger was longest in fifteen, the difference varying from 2 to 14 mm. ; in three the fingers were of the same length; while in six the index was the longer, the difference being from 2 to 6 mm. Prof. Ecker has further found the "ring" finger longest in casts and in several photographs of the hands of negroes; but in the hand of a "Turco" negro the index was the longer of the two digits. In photographs of a ring" finger Hottentot and of an Australian female, the was the longer, while in a photograph of a female Sandwich Islander the reverse was the case. "Einige Bemerkungen über einen schwankenden Character in der Hand des Menschen." Archiv für Anthropologie, viiier Bd. s. 67. ↑ Such as the Orang, Gorilla, Chimpanzee, and Gibbons. 3. As for Europeans, no conclusions have as yet been arrived at; but it appears probable that there is a relatively greater length of the index finger in the female than in the male sex; and further, among the latter, in the slight and highly developed, than in the short and underset. 4. Lastly, as regards Art. In that which is left to us of the productions of the ancients, there are variations in the relative length of the two digits, though it appears that the index finger, and especially so in the female, ought to be the longest. In the Dying Gladiator the index (of the left hand supported upon the knee) is the longer; while in the Apollo" Belvedere" (right hand) there is no appreciable difference. In the Venus "Medici,"* in the Venus pudica" of the Gallérie Chiaramonti, in Rome, as well as in the Venus by Praxiteles, in the Vatican, the index is In modern art there seems to be obviously the longest. no evidence of rule or canon; among painters, for instance, It is not probable that a difference in the length of the It may be concluded, then, that- a. In the Apes as yet examined, the difference being least marked in the Gorilla, the index finger is the shorter. B. In Negroes, also, the index appears to be the shorter. No sexual difference can as yet be established. 7. In Europeans the variation is so great that at present no rule can be laid down. d. When a great artist has attempted to represent a beautiful and ideally perfect hand, he has never made the May it then not be possible,index strikingly shorter than the "ring" finger. 1. That an index relatively longer than the "ring" finger is the attribute of a higher form of beauty? + 2. That here, as in many other particulars, the female form appears to be morphologically the purest? The longest and least mobile finger is the middle one; the shortest, and most capable of motion, is the thumb, or "pollex;" next in order in the scale of mobility come the little, "ring," and lastly the index, or forefinger. The question which Prof. Ecker has here raised, and into which he intends to inquire further, may appear to some trivial and unworthy of serious study; but, far from this, the satisfactory solution of it will, there is but little doubt, be of the greatest interest not only to the philosophical anatomist, but also to the sculptor and painter who would fain go a little below the mere surface of his art. It is certainly a subject in which, were they yet JOHN C. GALTON alive, such men as Goethe and Winkelmann would take the deepest interest. *The famous Medician Venus has been said to be a copy by Cleomenes, a son of Apollodorus, of the Venus of Cnidos, by Praxiteles. Vide Winckelmann's "Geschichte der Kunst des Alterthums."-J. C. G. same series. The hands of the writer are, unfortunately, specimens of the lower type, each index being considerably shorter than the "ring" finger in the It is a curious fact that in each hand the radial artery at its termination, instead of plunging beneath the volar muscles, takes a superficial and somewhat dangerous course as far as the skin web which passes from the pollex to the index. It would be interesting to know whether these phenomena are correlative or not. HE SCIENCE IN GERMANY He (From a German Correspondent.) ERR NEESEN, assistant, to Prof. Helmholtz, has recently published a memoir on the phenomena of attraction and repulsion by light and heat-rays, observed by Mr. Crookes. He states in it that he had already for two years observed such phenomena, which at first seemed to be a case of mechanical action of light-rays, i.e. of the effect of their impinging and rebounding on the surface of a mirror suspended by a cocoon-fibre. now thinks, however, from the experiments he has made, that the effects of light and heat-rays in question are to be regarded as merely produced through air-currents arising from heating of the air in certain parts of the apparatus in which the movements of the mirror take place. Neesen first shows that in the phenomena observed such air-currents have, in fact, influence. He used for his experiments a rectangular case of sheet iron, in the upper cover of which was a peculiar arrangement for hanging a cocoon fibre. In the lower part of one of the sides of the case was a rectangular aperture closed by a plane parallel glass plate, and behind this plate was the suspended mirror. The air-currents above referred to arise not only from the fact that the air in contact with the glass plate through which the light must pass to reach the mirror, or the air in contact with the mirror, is heated. The air-particles also between glass plate and mirror are heated by conduction of the heat; and so, by their heating also, air-currents are produced which tend to turn the mirror. In favour of Neesen's explanation are the facts (1) that the movements of the mirror always decrease when the air in which it is enclosed is rarefied; and (2) that these movements also become less if adiathermanous substances (eg. a column of water) absorb the light-rays before these can reach the mirror. The considerations which seem to be against his explanation are the following:-(1) The reversal of the movement, observed by Mr. Crookes, on a certain small air pressure being reached; (2) a fact appearing from Neesen's own experiments, viz., that according as the direction in which the light-rays fell on the mirror was varied, was the direction of rotation of the mirror changed, though the light fell on the same part of the mirror. Both these peculiarities, however, may also be explained by aircurrents. First, as regards the fact observed by Neesen, it is clear that, according as the lamp is placed to one side or the other of the mirror, different parts of the glass plate in front are heated, and different parts of the airlayer between glass plate and mirror; and accordingly the currents and the rotation of the mirror must have an opposite direction. To explain the reversal of the motion on a certain low pressure being reached, Neesen calls to mind that the conductivity of air for heat, as Kundt and Warburg have shown, decreases with extraordinary rapidity on decrease of pressure (well observed with low pressures); so that with as perfect a vacuum as possible, it entirely disappears, and only radiation of heat remains. Now, as long as the heat is conducted, the air-particles conducting the heat are themselves heated. On the other hand, no such heating takes place when the heat passes only by radiation. That with such very different conditions the currents may be different is probable in a high degree. W. MÜLLER ON BEES AND FLOWERS* IN N this communication Dr. Müller calls attention to the interesting facts presented by various groups of Hymenoptera, in which we find a series of forms presenting more and more complex life relations, accom "Die Bedeutung der Honigbiene für unsere Blumen," in the Bienen Zeitung for July 15. panied by a higher and higher mental organisation. The consideration of these gradations is calculated to throw much light on the question, "How has the Honey Bee acquired its remarkable instincts?" a question which the study of that species alone would, in his opinion, do little to solve, but on which the habits and organisation of other groups throw much light. The Sawflies (Tenthredo) are amongst the lowest of Hymenoptera. They merely choose a plant of the species on which they have themselves lived, cut a hole in the leaf with their curious saw, and deposit therein an egg. The young larvæ thus find themselves on their food and live like ordinary caterpillars, which in general appearance they much resemble, and like which they are exposed to destruction by various enemies. Passing on to the Gall Insects (Cynips), we meet with a new mode of life which is very instructive. The incision made in the plant by the Sawfly causes little abnormal growth, while in the case of the Cynipidæ, on the contrary, it gives rise to the well-known galls. Some species, however, pierce not plants, but animals, and have thus opened out for themselves many more possibilities of existence, since there is scarcely any group of insects which is free from these attacks; neither the thick-skinned beetle, nor the active and powerful wasp, nor the woodboring larvæ of Cerambyx, nor even the aquatic larvæ of the Phryganeas. This passage from phytophagous to carnivorous habits has not only led to the formation of many new species, but also to a greater complexity in the relations of the parents to their young, and to a higher intellectual development, which is shown especially in the arrangements made for the nourishment of the larvæ, since it certainly requires both greater energy and more intelligence to discover and attack a particular species of insect than merely to lay an egg on the plant which has served the mother herself for nourishment. The passage from the gall insects to these insect-piercing species must, in M. Müller's opinion, have been slow and gradual. genus Synergus, which deposits its eggs in the galls of the true gall insects, constitutes, perhaps, a link between the two groups. The On the basis of this increased energy, intelligence, and adaptability, certain groups then made a still further advance by which some of the drawbacks incident to such a mode of life were avoided. For it of course frequently occurs that caterpillars and other insects in which these insect-piercing Hymenoptera have deposited their eggs, are devoured by birds or other enemies. Certain species, however, meet this danger by transporting their victims to a place of security. To effect this, however, certain conditions are necessary. The aggressor must be sufficiently large to overpower his victim, but the latter must not be killed, or it would decay and thus become unsuitable for food. Dr. Müller considers that many insect-boring species have probably endeavoured to secure their prey, but have under these circumstances found it impossible to do so. Thus, the ovipositor of the Tenthredo became the sting of the wasp, and thus those species which carried off their victim to a place of concealment would abandon the habit of laying their eggs inside the victim. Dr. Müller expresses the opinion that the various proceedings by which the solitary wasps thus protect their young against contingencies to which the insect-piercing species are liable, must have at first been arrived at with a consciousness of the object to be effected, but that they have gradually become instinctive, and are now unconsciously inherited from generation to generation. Still it is, he observes, impossible to watch a wasp at work without feeling that, with these inherited customs, or so-called instinct, much individual effort also comes into play. Dr. Müller proposes to discuss this interesting part of the subject in detail in a future communication. J. L. Nov. 4, 1875] NATURE FAYE ON THE LAWS OF STORMS* Mechanical Identity of Waterspouts and Eddies.-The question then is reduced to this, viz., whether, when in the middle of the most profound calm these destructive waterspouts are seen to appear, the form of which corresponds so well to the eddies formed in streams of water, we can point to any current by which the phenomenon has been originated. Now this is precisely what we intended to set in strong relief in describing the general currents of the atmosphere. The counter-trades clearly show that there exist above our heads unmistakable currents of air in motion. Without even recurring to considerations of this nature, it is enough to cast our eyes over the heavens on the appearance of a waterspout, in order to see by the march of the clouds that in spite of the calm below, powerful horizontal currents prevail aloft, which, as their different parts cannot advance at the same rate, must consequently give rise to whirling movements of a more or less decided character. If one of these whirls meet with the favourable circumstances so often seen in waterstreams, it will be regularly developed by taking the form which analysis assigns to it; by its downward movement it will even penetrate through into the calm strata, the resistance of which will gradually alter its form and its course, and end by reaching the ground. This simple notion of the mechanical identity of gyrations, whether of liquids or gases, furnishes at once the explanation of phenomena which meteorologists have laboured to find in an entirely different range of ideas. Waterspouts contain powerful forces in action, because they draw the force from a medium above, where it is in abundance; they march onwards because they follow the current which originates them; at their base they are slightly curved, not forwards but backwards, because the comparatively still medium they traverse offers a certain amount of resistance; they act nevertheless in the same manner both on the ground and over water, whatever be the curvature of the conical tube which descends from the clouds, because this curvature never interferes with the direction of the axis of rotation of each spiral, but only with the succession of these spirals in space, &c. This identity of waterspouts in air and of eddies in water, which is so complete in a mechanical and geometrical point of view, is no longer to be looked at altogether from the physical standpoint, on account of the differences which in this respect exist between water and gas. Indeed, the temperature of a stream of water is almost the same at all depths; in the air, on the contrary, heat decreases markedly as we rise to the higher strata. Further, the moisture of the air is liable to be condensed for a fall of temperature often very slight. Thence the cold air of the high regions, drawn gradually downward by the whirling movement into the low and moist strata, generates a thin mist all round the waterspout. This mist serves as an outer envelope or sheath, the form of which is more or less sharply marked, being rendered visible by its opacity. There is no doubt that the air in its descent is subjected to an increasing pressure and gradually rises in temperature; but it is lower than the temperature of the surrounding air, and it is enough if it falls to the dew-point of the general mass of air surrounding it in order that the nebulous sheath may be immediately produced. If the difference of the two temperatures is insufficient, or if the humidity is too low in any particular stratum, the misty sheath will not be formed, and the waterspout will in part be invisible. None the less, however, will it be there, though it seem cut in two, or appear only in its upper part in a truncated form. This is the appearance so often presented by waterspouts at their commencement, when the upper and lower portions are seen, but not the intermediate portion. Soon these detached portions meet, the outside sheath * Concluded from vol. xii. p. 538. completing itself as the stratum traversed by it becomes Just as happens in the case of the water which gradually A As the purely physical appearances of waterspouts differ widely from each other, some have failed to observe the slightest trace of an internal movement; others have attributed to them a descending movement without rotation; and lastly, others, and these the most numerous attribute to them a whirling ascending movement. little reflection easily explains these contradictions. What is seen and what is related by eye-witnesses whose impressions are vitiated by old-standing prejudice, has no reference to the waterspout itself, which, like air, is transparent and invisible, but to its external envelope of mist, which is more or less opaque. The envelope is exterior, we repeat; it does not therefore partake in the internal gyrations, which, moreover, are too rapid to be visible. Only the surrounding air which is brought into contact with the waterspout is rapidly drawn from some distance The by lateral communication with the whirling movement, the result of which is a sort of whirling or spiroidal agitation in the outside sheath of the waterspout. well known. It is thus that the slight movements of the degree in which movements of this sort favour illusion is cilia of rotifers have the appearance of a rapidly revolving wheel, and the simple rotation of a spirally-cut cylinder of glass produces the impression of a flowing stream of water. Further, the air which is thrown out at the base rises again outside the waterspout. The aqueous vapour imperfectly condensed in the outside of the sheath has itself an ascending tendency sufficient to raise some of the small cloudlets of mist found there. Here are the real movements, complex and changing, but slow enough to be visible. The illusion of the observer lies in attributing to the interior of the waterspout the movements which really take place round and outside its exterior margin. The part played by electricity has been thus stated by Peltier, who supposed he had detected traces of this force in the well-known waterspout of Monville. The sheath of vapour is in some sort a continuation of the electricallycharged clouds; it forms a long conductor of about eight hundred feet between the clouds and the ground, a conductor doubtless very imperfect, but on a great scale, and capable of affording to some extent a passage to the electricity. It is, however, far from being comparable with the destructive characteristics of the thunderbolt. The way in which trees overturned by whirlwinds are sometimes broken up has been recognised as resembling more or less that of trees struck by lightning and shattered into splinters; but this effect is only the result of the violent torsion exerted by the gyratory movement of the whirlwind, and not of the sudden passage of an electrical current. Men and animals have often been caught by whirlwinds and injured, without ever experiencing the least electrical shock. Thus the essential characteristic of these remarkable movements which produce waterspouts or great tornadoes is a circular gyration, the spirals being slightly inclined to the horizon. Wherever you make a section of it, you only find there concentric circles with the radii always converging towards a centre. In representing them geometrically you need not hesitate between the circular diagrams of Reid, Redfield, and Piddington, and the diagrams with converging rays of some learned meteorologists, the victims of a hypothesis and old prejudice. The former diagrams reproduce the mechanical phenomenon in its essentials; the latter answer to a mere illusion which a little reflection should ages since have exploded. Extension of this Identity to Cyclones.-The last step only remains to extend these conclusions to great tornadoes, that is, typhoons, and lastly to cyclones, which often overspread a vast extent of territory. It is one of the characteristic properties of the eddies generated in currents of water, that they are formed on every scale, even the largest, without undergoing any essential change. Eddies may be a few inches in diameter, a few yards, a few furlongs, or even of still larger dimensions; it is the breadth of the currents where they are generated which alone limits their size. In the ocean there are gyrations on a still vaster scale, or even on a scale altogether colossal, such as the vast currents of the Atlantic which circle round the calm region of the Sargasso Sea. The sun presents the phenomena of whirling movements still better defined and of all dimensions, from large openings equalling our cyclones, even to those large spots which are five or six times greater than the earth itself. In like manner, in the whirling movements of our atmosphere are found small, short-lived eddies of a few feet in diameter, whirlwinds and waterspouts, which last longer, from 10 to 200 yards across, and tornadocs from about to 1 mile in diameter. Beyond this the eye cannot take in the forms of the whirling columns; these receive another name, but in all essential points they remain the same. When the dimensions are still greater, the diameters measuring 300 miles and upwards, they bear the name of hurricanes or cyclones; but notwithstanding this, their mechanism remains unchanged. They are always gyratory, circular movements increasing in velocity as they near the centre; are generated in the upper currents of the atmosphere, through the inequalities of their velocities; are propagated downwards through the lower strata in spite of the calm or independently of the winds which there prevail; ply their destructive energy when they reach the obstacle offered by the ground; and follow in their march the upper currents, so that the track of their devastations marks out on the surface of the globe the route of the viewless currents of the upper regions of the atmosphere. There is, however, a difference between whirlwinds and tornadoes on the one hand, and typhoons and hurricanes on the other. As regards the former, note in the first place, the upper portion (embouchure), which is a sort of truncated cone inverted and very much widened out above, and in the second place the descending column which prolongs the meteor even to the ground. If the atmosphere was a gaseous mass of air of indefinite height like that of the sun, cyclones would always present these two features. As regards cyclones, however, the ground is very near in proportion to the extent of area they cover, and is reached before they can be subjected to the prolonged contracting process scen in waterspouts and whirlwinds. A cyclone is then a vast whirlwind, but · reduced by the obstacle offered by the ground, to the upper part, or to what may be called the funnelshaped portion of the phenomenon strictly so called. Thence, doubtless, the constant presence in the former of a calm space about the centre, of which the analogue is to be found only in the circling movements of the ocean on their grandest scale; and thence also certain important peculiarities of cyclones to be more particularly insisted on, after having examined the movements of translation of these phenomena. Course of the Upper Trade Winds.-When the attention is directed to whirlwinds which appear most frequently to be accidental phenomena of short duration and merely superadded to other phenomena of a more general character and much more lasting, it must be allowed that the short lines marking out their course have scarcely been studied from a geographical point of view. These lines probably follow no simple law. In this respect it is otherwise with cyclones; their course recurves, as we saw at the beginning of these articles, on the globe in accordance with a particular law the constancy of which Fig. 2 (vol. xii. p. 402) reveals at a glance. From this chart, the upper currents, whence cyclones derive their origin and mechanical power, do not proceed directly from the equator to the poles. They are deflected at the outset toward the west, then toward the east, thus describing over the surface of the globe parabolic curves whose apices lie somewhere within a few degrees of the polar limits of the surface trade-winds. Clearly these upper currents, which are true aërial rivers, ought to form a part of the upper trades whose existence is assumed, but their actual course is not directly known. If this assumption be correct, then Fig. 2 presents at once the projections of the double system of trades and countertrades over both hemispheres; and it only remains to explain the singular recurving course taken by the upper trades. This explanation we shall attempt, though the question lies a little out of our way. If the atmosphere were withdrawn from the influence of the solar heat, it would remain in equilibrium ; its successive strata would arrange themselves according to surfaces of level, and would become part and parcel, so to speak, of the solid globe itself; at least it would, even as regards the highest strata, exactly follow the earth's rotation. The effect of the solar heat is constantly to disturb this equilibrium, by the introduction of movements which are the more curious inasmuch as they do not essentially destroy the normal stratification of the strata of the atmosphere. The air incumbent over the hemisphere actually facing the sun is expanded in its lower strata, where the opacity arising from dust floating in the air, and above all the aqueous vapour, absorbs a large part of the heatrays of the sun. The intervention of this aqueous vapour which ascends vertically from stratum to stratum, has in a special manner the effect even of rendering the diurnal variation of temperature perceptible at heights at which it would not be felt if the air was dry. The maximum of this general dilatation in the torrid zone takes place under the vertical rays of the sun. In this manner the centre of gravity of the lower strata rises vertically; these raise the strata above them, which being specifically lighter, dry and transparent, are consequently less sensitive to the sun's rays. All the strata in succession, thus thrust upward above their surface of normal height, tend to flow with accelerated motion along these surfaces in the direction of the two poles, where the temperature is relatively low. This effect is still further increased by the peculiar march of the aqueous vapour which is principally condensed about the poles, whence it returns to the equator by another way than that of the atmosphere, viz., along the surface of the earth in the liquid state. The atmosphere cannot exactly follow the diurnal rotation. A half of its mass, or from about 30° lat. S. to 35° lat. N., lags somewhat behind, since all the molecules in this region being thrust upward describe circles continually increasing in size with the linear velocity from the lower level from which they started in their ascent. To this retardation must be superadded that of the surface trades resulting from their general flow towards the equatorial region. Beyond the tropics, on the contrary, in the temperate zones where the air advances into parallels of latitude continually diminishing in size, the other half of the atmosphere flows in advance of the earth's rotation. Towards the polar circles this advance is converted into a circling movement round the two poles from west to east. The unequal distribution of land and water over the globe modifies this general aërial current, so that it does not flow on in one current, but is broken up into many currents-the equalities of the surface throwing the current of the counter-trades into several currents more or less distinct from each other. We can easily imagine the behaviour of the counter-trades by combining their march toward the poles with the two opposite transverse tendencies of which we are about to speak. Between the tropics, the resulting currents do not blow straight to the equator, but wear round more toward a westerly direction. Beyond the tropics, they do not blow directly toward the poles, but take a course inclined more to eastward. The two following figures will explain our meaning: Fig. 13 represents the whole upper currents for both hemispheres on a projection of the meridian; and Fig. 14 for the northern hemisphere on a projection of the equator. The dotted arrows mark the surface countercurrents; in other words, the trade-winds blowing obliquely towards the equator, making nearly a right angle with the upper trades of the torrid zone. A slow whirling movement may also be seen around both poles resulting from the counter-trades. These really exist, for the meteorologists of the United States have recently described them under the name, a little fanciful, perhaps, of polar cyclones. The aerial rivers which are marked out in the midst of these great movements, by which the equilibrium, incessantly disturbed, tends constantly to re-establish itself, exhibit then precisely the course which we have recognised as a peculiarity of the trajectories of cyclones, whilst the surface-trades have no relation to these same curves showing the courses of cyclones. This agreement is a further proof that cyclones must have their origin in the upper FIG. 14. regions of the atmosphere, and thence descend even to the ground, and in doing so traverse strata of air either calm or in motion, in such a way as to be totally independent of the cyclone a state of things incomprehenAs to the direction of rotation of cyclones, it results from sible on any other hypothesis that has yet been advanced. it that, in these currents strongly recurved, the velocity goes on diminishing transversely from the concave side to the convex side. The zone of calms would then no longer accord with the phenomena of an ascending updraught, but with a maximum of dilatation to the right and to the left of the place where the movement toward the poles commences. Lastly, the mean velocity of these currents, feeble at first in the neighbourhood of the equator, would go on accelerating just as the velocity of translation of our cyclones. Segmentation of Cyclones.-Whatever may be thought of these opinions regarding the march of the upper trades, of which the surface-trades are the counterpart, it is impossible to doubt that cyclones take their origin from these currents. Let us then look more closely at these gyratory movements. If the maximum height of these trades be from 33,000 to 40,000 feet, and the lower diameter of the gyratory movements, or cyclones, where they meet the ground, from 120 to 180 nautical miles, it will be seen that cyclones must have a figure very different from waterspouts and tornadoes, whose proportions are altogether different, since the height of these last is enormously disproportioned to their lower diameter. Piddington was therefore right in comparing cyclones to mere whirling discs. It would however be more correct to regard them as waterspouts reduced to their upper funnel-shaped portion, or deprived of their slightly conical column, which descends even to the ground. As it advances, the generating current is lowered a little; the vertical height of the cyclone is thereby as much diminished, its section enlarges by contact with the ground, and the disc becomes even more flattened out. This being granted, if any whirling movement encounters resistances, or if the general current exhibits differences of velocity in different places, it is in the upper regions of the atmosphere especially that these disturbing causes will act most powerfully on the phenomenon, because the velocities are there less, and the distances traversed by the currents enormous. Below, on the other |