transcendental mathematician chooses to demonstrate by formulating on the basis of imaginary data.

But in this case we are not entirely dependent on formulæ, as the heat communicated to a meteoric body in its journey from cosmical space to the surface of our earth can be demonstrated by facts.

Masses of meteoric iron do actually come from outer space and plunge through our atmosphere, just as the hailstones are supposed to come and to plunge by Schwedoff; in doing which, they must, according to Sir William Thompson, generate the above-named amount of heat and be subjected to its operation.

To understand this, we must remember that the specific heat of water is (in round numbers) nine times as great as that of iron, i.e. an amount of heat-producing work required to raise a given weight of water one degree will raise the same weight of iron nine degrees, or nine times as much iron one degree. Therefore if the water be raised 33,000°, as Sir W. Thompson affirms, the iron wlll be raised 33,000 × 9=297,000 degrees. But iron fuses at the modest temperature of 1,600° Cent. (according to Pouillet), and is vaporised at somewhat above this. How, then, do these meteoric masses perpetrate the "manifest absurdity" of reaching the earth in a solid state?

The reply is the simplest possible, but has nevertheless escaped the mathematicians. Let the reader hold one end of a poker and place the other in a bright fire, or do the like with a shorter piece of iron. He will learn thereby that one end of the poker may be red-hot while the other is pleasantly cool, or, in other words, the conduction of heat even through metals is a work of time-is not instantaneous.

But the passage of a meteoric stone through our atmosphere at the enormous velocity supposed by Sir William Thompson is completed in a fraction of a second—a very small fraction, if it descends perpendicularly. Therefore, no matter how much work may be done on the surface of a solid meteorite of any considerable magnitude, its interior will remain cold during its fall, although its surface be volatilized or dissociated, or any otherwise affected by the heat evolved.

There is a splendid collection of meteorites in the British Museum, some of them cut through to display their internal structure. They all indicate superficial fusion, or, I may say, refusion, such as would occur if intensely heated superficially in their passage through our atmosphere. Large hailstones are similar. They are composed of snow-like crystals in the centre, and surrounded with a surface of ice such as would be produced by the melting and regelation or welding of such crystals,

If this be the case with so good a conductor of heat as metallic iron, how much more so with a mass of ice, which of all known solids is about the worst conductor of heat. But the reader may say that the melting of ice demands far less heat than the melting of iron. This is true, but under the conditions of great heat generated by surface friction the heat must not only melt the ice but evaporate the water. Adding the latent heat of water to that of steam, and allowing for the high specific heat of water, it will be found that more than three times as much is required to vaporise 1 lb. of ice as to melt 1 lb. of iron. Quantity not intensity of heat, i.e. heat-work, not mere temperature,

is here considered.1

This seeming paradox will appear less paradoxical if the simple experiment is tried of placing in the midst of a fierce fire a piece of ice and a piece of iron of same weight, and watching the effects of each on the fire. The ice will melt less rapidly than might be supposed, and its effect of robbing the fire of its heat will be strikingly displayed by the blackening of the glowing coal around it. The ice will do much more than the iron. Of course the iron should be of the same temperature as the ice.

A reply to my view of the subject may possibly be made by asserting that, as the evolution of heat is proportionate to the work done in arresting the mechanical motion of a body, the whole of the body whose motion is arrested will be heated accordingly. Such an assertion would not be inconsistent with the views of thermodynamics which are expounded in some of our text-books. If it is made, I will discuss it in a future Note.

NOT

"WATER, WATER EVERYWHERE."

OT only has the idea of meteoric hailstones been treated rather scornfully, but that of the universal diffusion of water through space in any form has been similarly handled.

On the other side are the following facts. Water has been proved to evaporate into air of every degree of attainable density, and into the most complete vacuum that modern refinements of the Sprengel pump, aided by chemical absorption, can produce.

The following are the figures, stated in degrees of Fahrenheit: Latent heat of water 142°, of steam 966°. To convert the ice at 32° into water demands 142°, to raise this to boiling point 180° more, making 322°; add to this 966° for conversion into steam, and we have 1,288°. This multiplied by 9 gives 11,592°. The melting point of wrought iron, according to Daniell, is 3,280°; three times this leaves sufficient latitude to allow for the unknown latent heat of liquid iron, which is certainly but small,

The compression of the air or the refinement of the vacuum makes no difference as regards the quantity of vapour that ultimately passes into a given space from a surface of liquid or solid water. This quantity is simply a function of temperature. It is not the air or other gas above the water that is saturated, but the space. Until such saturation is completed, the evaporation of the water continues.

What, then, must happen to our ocean? What must happen to the water we see on the planet Mars, to the vapour of water the spectroscope displays around the sun, and indicates on Venus, Jupiter, and the other planets?

These waters must evaporate into interplanetary and interstellar space until that space is saturated, the amount required for such saturation depending on its temperature. If it were not already saturated, our ocean would dry up and leave this world as barren as the moon, and there could be no snows deposited around the poles of Mars, nor vapour accumulated in the solar atmosphere.

THE VOICE OF LIZARDS AND FROGS.

HIS subject has recently been discussed in Nature, and Mr. S. E. Peal writes from Assam, describing the curious cry of the gui or gooee lizard, about 3 to 3 feet long, which is named from the sound it makes.

The slow-worm has a voice, or makes a clacking or chirruping sound with its mouth, which I can hear distinctly at a distance of five or six yards.

Common English frogs, although usually silent, scream piteously at times. I first observed this some years ago when, in my Birmingham froggery, an ill-fed monster specimen seized a smaller brother by the hind legs with cannibal intent. The screams of the victim brought me to the rescue. They scream in like manner when seized by a duck, but not when wounded by a blow. I have seen cases of sad accidental mutilation by scythe and spade where no sound was uttered. From this I infer that fear or mental horror is the chief source of the cry.

W. MATTIEU WILLIAMS.

TH

TABLE TALK.

A CREAM-PRODUCING MACHINE.

HE opportunity was afforded me while recently in Berlin of contemplating a novel and curious invention, the introduction of which into London can be only a matter of time. This consists in the cream-extracting machines of Lefeldt and Leutsch, at present at work in the establishment of Herr Bolle, a not inappropriate name for one dealing in milk. The principle of these machines rests on the application of centrifugal force. Milk, as it comes from the cow, is put into a species of drum, which is kept rapidly revolving; the milk, as the heavier portion, flies to the outer circumference and is collected by a species of lip; the cream, which is lighter, falls to the inner circumference. The establishment of Herr Bolle is not unlike an English sugar refinery. The milk, lifted into tanks on the top floor, falls by gravity into the creaming machine. Two or three qualities of cream are extracted. The thickest quality goes to the confectioners, and the second quality to hotels. Butter and cheese are made on the premises, and the skim milk is sold at twopence a quart. What is not required for human consumption is converted into a species of condensed whey, which is useful for feeding horses. 120 of these machines are now, I am told, in use in Germany. About 35,000 litres of milk are, when the eight machines in employment in Berlin are in full work, dealt with per diem.

M

AN ACTOR ON ACTING.

R. BOUCICAULT'S address upon the art of acting delivered recently at the Lyceum Theatre inspired much amusement and some interest. An audience, consisting almost entirely of those connected with the stage or the drama, assembled to hear one of the most competent of modern actors explain the mysteries of the art he practised. In a certain sense, the result was necessarily disappointment. All the charm of an exquisite method was employed to dignify elementary information and to ennoble commonplace. Very humorous was it to see Mr. Boucicault's illustrations of what is grotesque in acting,

and it was no less agreeable to hear him denounce the overweening conceit which is the chief obstacle in the way of almost every actor. No lesson was, however, obtainable except that what is rudimentary in art may be taught. To establish that fact needed neither "ghost from beyond the grave" nor actor from beyond St. George's Channel. In his condemnation of some vices of English speech, and especially our customary omission or mispronunciation of the letter r, Mr. Boucicault scored at our expense.

ON

TRAGIC ACTING.

NE point raised by Mr. Boucicault was inadequately treated. What seems unnatural in tragic delivery is, Mr. Boucicault holds, attributable to the fact that the sentiments and language of tragedy are unnatural, and that ordinary pronunciation seems out of keeping with the style of composition. So far as it extends, this assertion is true. Much more requires to be said, however, in order to furnish a full explanation. The blank verse of English tragedy demands a special form of declamation, and without it the whole spirit of tragedy would be lost. So soon as realism penetrates into tragedy, tragedy itself will, so far as the stage is concerned, expire. The delivery of the tragedian is, however, a direct transmission from the time when tragedy was a choral service, and as such was a chant. Constant attempts have been made to modify this, and a great change in the end has been made. So strong, however, is the influence of tradition, that something of the colouring yet survives, and is distinguishable in every actor that ever trod the stage. In the seventeenth century Molière censured the monotonous delivery of tragedy, and his associate Baron, prompted by him, made some attempt to reform it. In subsequent years many actors, both French and English, introduced further changes; Le Kain, Talma, and Hackel in France, and Edmund Kean in England, being chief agents in the reformation accomplished. That the old influence is not entirely subdued is, however, sufficiently apparent to those who listen to Mdlle. Bernhardt in "Phèdre," or Signora Ristori as Lady Macbeth.

RESEMBLANCE BETWEEN THE 15TH AND 19TH Centuries.

E

XACTLY analogous to the great Renaissance age is the age in which we now live. Never since the beginning of time was there a period when intellectual life was more keen, or when more brilliant discoveries came to benefit or to dazzle mankind. Fairy