Page images
PDF
EPUB

What would happen to these animals if carried round by the current above described, and swept from their native clear sea-water to the turbid and brackish outflow of the Stour? All but the coarse muddy-gilled cockles would die, and falling where we find them would coat the clay bank of the shore with a deposit of their shells.

I found living cockles in abundance, but where the empty shells are most abundant, saw no living specimen of the more delicate species. A few of these made their appearance on passing the shelly limit when proceeding towards Deal.

REGELATION AND WELDING. M OST of my readers are doubtless more or less acquainted

IVT with the phenomena which are usually described as “regelation,” or refreezing. If two pieces of ice are pressed together when at or near their melting point, they unite and become one piece. If many pieces are thus treated, the same, of course, occurs. Thus snow particles may be compressed into a solid mass of clear transparent ice, as they are on a great scale in the formation of glaciers. My own method of illustrating this is to place fragments of ice or snow in a little iron syringe, the piston of which is forced down by screw power. This shows, firstly, the uniting of the fragments, which form a clear cylinder easily removed, and this cylinder is about half. an-inch in diameter. When returned and further compressed the ice is squirted out as a long continuous transparent stick of the thickness of vermicelli, or ordinary ever-pointed-pencil “leads,” for the making of which the syringe was constructed.

Another very pretty and well-known experiment is to take a block of ice and support it at both ends, then pass over the middle a copper wire to the ends of which weights are attached. The wire being warmed by the air around, and conducting the heat, cuts gradually through the ice, but the cut heals itself almost as fast as the wire descends.

The accepted explanation of this is that the pressure thaws a portion of the ice and that some of the water thus formed refreezes. This theory is based mainly on the fact that pressure lowers the freezing-point of water, and therefore it is inferred that at the points of contact a certain degree of thawing is produced at the moment of pressure, and that on the removal or diminution of this pressure the opposite occurs and the water is refrozen. But we must not omit to consider the quantity of effect due to pressure. A pressure of fifteen pounds on the square inch (as shown by recent researches of Dewar) reduces the freezing point by only o‘0072°, or a trifle more than yooo of a centigrade degree.

But there are many substances that behave in the opposite manner to water, their freezing point being raised by pressure. Wax, for example, has its solidifying point raised ten whole centigrade degrees (from 647 to 74:7) by one atmosphere of pressure ; that of spermaceti is raised from 51° to 60°; of stearine from 67.2° to 68-3°, and of sulphur from 1079 to 135°C.

But all these substances exhibit all the phenomena attributed to the so-called regelation. Faraday's celebrated experiment of floating several pieces of ice in water then bringing them in contact while thus immersed and showing that they all stick together, may be repeated by placing lumps of solid wax in melted wax (at about the melting point) and treating them in the same manner.

Everybody knows that two pieces of sealing wax raised to near their melting point stick together if made to touch each other, and unite as one if pressed together. The same is the case with iron, with platinum, with glass, and every other substance that melts gradually or softens before becoming fluid. All such substances are weldable, or, in common language, they "stick together," when softened.

It is only when ice is thus near its freezing point that it can be welded, as everybody knows who has tried to make a snowball with snow at ten or a dozen degrees below the freezing point.

The squirting of ice in the experiment above described proves that it has the viscosity possessed by wax, pitch, iron, glass, &c. &c., when approaching their melting points, and therefore that it should be simply weldable or-pardon the word-sticktogetherable; which word, however heterodox, is not worse than regelable.

These views of the subject, which I published some years since, are further illustrated by some recent experiments of W. Spring. He has imitated the regelation of ice by compressing similar crystalline substances, such as sodium nitrate, which, when coarsely powdered and subjected to sufficient pressure, “unites like drops of water.” Lead filings, powdered bismuth, zinc filings, aluminium filings, copper, antimony, &c., in like condition, were similarly made to cohere.

It has long been known that a leaden bullet, cut in half, may be reunited by even a moderate pressure, if the cut surfaces are clean and bright. In all these cases it appears that when near the melting point the amount of pressure required to effect the welding is small, and it increases at lower temperatures, but that even where low temperatures are compensated by very high pressures, the welding is preceded by a softening similar to that which precedes fusion by heat. When lead filings were subjected to a pressure of 2,000 atmospheres they united "into a uniform block, which under the microscope exhibited no trace of the original filings, but looked like a block of cast lead.” “At a pressure of 5,000 atmospheres the lead oozed out at all the joints of the apparatus as if it were liquid."

THE VOICE OF WATERS. In the course of a walk in Switzerland, when bathing in the

1 Rhine a little above Basle, a curious hissing sound was audible whenever my ear was near to the surface of the water. It is described in my diary as resembling a chorus of chirping grasshoppers, which choruses are very common thereabouts in the summer time. On immersing my head, this hissing became a roar, like that of breaking waves on the sea-shore.

The river at this part is a smoothly-flowing stream, such as we usually regard as quite silent; but the water flows over a floor of rounded pebbles, and the current is just strong enough to move some of them. It is therefore probable that the hissing sound is due to the movements of those in the immediate neighbourhood. But will this explain the roar which I heard under the water ?

I think not, as no accumulation of hissing can produce a deeptoned roar. M. Colladon long ago made a number of experiments on the transmission of sound by water. He found that it travelled with a velocity of 4,708 feet per second (against 1,120 feet in air of the same temperature), and that a bell rung under water in the lake of Geneva could be distinctly heard, with the head immersed, at a distance of nine miles. The roar that I heard in the seeming silent river was probably that of the rapids some three or four miles farther up the river.

I have since made other experiments of a similar kind; have heard the roar of a waterfall, by immersing my head in the rivulet it formed, at a distance where no sound was audible in the air.

As I find these Science Notes quoted in American papers, it is evident that they are read on the other side of the Atlantic, and I therefore suggest that such experiments should be repeated on the Niagara River below the falls. I have no doubt that they will be distinctly heard at the mouth of the river, fourteen miles away, and far on into Lake Ontario. This qutspread of still water affords a fine field for the experiment,

W. MATTIEU WILLIAMS,

233

TABLE TALK.

RABELAIS. THE statue of Rabelais, which I have on more than one T occasion spoken of as in preparation, has now been erected in Chinon, a town of Touraine, which claims to be the birthplace of the great Renaissance teacher. Less stir than might have been expected has been made in France, while in England few newspapers have done more than mention the event. For myself, I hope before many weeks are over to make a pilgrimage to Chinon, which, apart from its associations, is one of the most pictureque towns in France. I am anxious to know which of the two types of face, utterly different if equally authoritative, which are found in France, has been em. ployed by the sculptor. The features of Rabelais are not, I might suppose, easy to sentimentalise, yet the effort has been made. I have seen half-a-dozen oil paintings of Rabelais, all of them claiming to be original. The most characteristic head is, however, that on a maquette of Noël Ruffier. Here alone do I find the mingling of the intellectual and the animal, which fits the great apostle of Pan. tagruelism, the high-priest charged to deliver the mystic revelation of the Dive Bouteille.

"LE LIVRE.” LOR a sight of the model of Rabelais of which I speak, I am T indebted to Le Livre, in which an engraving of it appears. Except in this shape, the work is unpublished. I wonder how many of my readers are familiar with Le Livre, the most luxurious and scholarly periodical which has yet been devoted to bibliography. A set of it, from the beginning, in 1880, graces my shelves, and forms a storehouse of information and delight. Some of the best and most characteristic writing of men like M. Champfleury and Le Bibliophile Jacob appears in its pages, and the editor, M. Octave Uzanne, to whom is owing the recently published volume L'Eventail, which is an absolute marvel of French typographical and illustrative art, is responsible for many delightful bibliographical sketches and studies. I have long sought an occasion to draw the attention of my readers to a work which every lover of books and student of bibliography is bound to possess, and which as yet has failed to obtain in England the reception it merits.

DID ROBESPIERRE COMMIT SUICIDE ? W A S the wound of Robespierre received on the famous neuf

Thermidor self-inflicted, or was it due to the gendarme Méda? Thiers states distinctly, “Robespierre decided at length to put an end to his career, and found in this pass to which he was given, courage to kill himself. He discharged a pistol at his head, but the bullet, entering below the lips, pierced his cheek, and inflicted a wound that was scarcely dangerous.” (“ Histoire de la Révolution Française,” livre 23.) Carlyle draws a picture of Robespierre “ sitting on a chair with pistol-shot blown through not his head, but his underjaw; the suicidal hand had failed ;" and says, concerning Méda's assertion that it was he who shot Robespierre, “ Few credited Méda in what was otherwise incredible.” On the other hand, M. Léo Joubert, in the “ Nouvelle Biographie Générale," summing up the conclusions of various historians, is not even at the trouble to men. tion the report of suicide. His words are, “ Robespierre was seated in a fauteuil, his left elbow resting on his knee, and his head resting on his left hand; before him were seven papers, among which was, stained with his blood, an appeal to insurrection, which bears only the first two letters of his name. Méda, upon seeing him, discharged a pistol at him and broke his lower jaw.” So carefully written are the articles in the “Nouvelle Biographie Générale," that a statement like this may almost be accepted as conclusive. The question whether Robespierre attempted to commit suicide has been mooted of late in the English as well as the French press, and La France reproduces the deposition of Méda, in which he claims to have fired the shot.

• THE STATEMENT OF MÉDA CONCERNING ROBESPIERRE. THE younger Robespierre, it is known, threw himself out of the

T window on the arrival of the assailants. Méda's words are, “ I knew the elder Robespierre ; he was sitting in an arm chairthis was in the hall of the Hôtel de Ville-having his elbow on his knees, and his head leaning on his left hand. I made a rush at him, and presenting my sword to his heart, said to him, ' Yield, traitor!' He raised his head, and answered, 'It is you who are a traitor, and I will have you shot.' At these words I took one of my pistols in my left hand, and, stepping one pace aside, fired at him. I intended to hit him in the heart, but the ball struck his chin and broke his left jaw.” Partly in consequence of this action, Méda was made a Colonel and a Baron of the Empire.

« PreviousContinue »