His first important production was Epitome elementorum physico-mathcmaticorum, 12mo, Leyden, 1726,—a work which was afterwards gradually altered as it passed through several editions, and which appeared at length (posthumously, edited by Ludolf) in 1762, under the title of Introductio ad philosophiam naturalem. The Physicae experimentales et geometricae dissertationes (1729) threw new light on magnetism, capillary attraction, and the cohesion of bodies. A Latin edition with notes (1731) of the Italian work Saggi di naturali esperienze fatte nelΓ Accademia del Cimcnto contained amid many other curious investigations a description of a new instrument, the pyrometer, which Musschenbroek had invented, and of several experiments which he had made on the expansion of bodies by heat. Musschenbroek is also the author of Elementa physica, 8vo, 1734 (English translation 1744 by Colson), and of papers in the Mémoires of the Paris and St Petersburg Academies, and in the London Philosophical Transactions.

The byssus is a collection of horny threads by which the Sea Mussel (like many other Lamellibranch or Bivalve Molluscs) fixes itself to stones, rocks, or submerged wood, but is not a permanent means of attachment, since it can be discarded by the animal, which, after a certain amount of locomotion, again fixes itself by new secretion of byssus from the foot. Such movement is, however, very rare. Mytilus possesses no siphonal tube-like productions öf the margin of the mantle-skirt, nor any notching of the same, representative of the siphons which are found in its freshwater ally, the Dreissena polymorpha. Mytilus edulis is an exceedingly abundant and widely distributed form. It occurs on both sides of the northern Atlantic and in the Mediterranean basin. It presents varieties of form and colour according to the depth of water and other circumstances of its habitat. Usually it is found on the British coast encrusting rocks exposed at low tides, or on the flat surfaces formed by sandbanks overlying clay, the latter kind of colonies being known locally as “scalps.” Under these conditions it forms continuous masses of individuals closely packed together, sometimes extending over many acres of surface and numbering millions. The readiness with which the young Mytilus attaches itself to wicker-work is made the means of artificially cultivating and securing these molluscs for the market both in the bay of Kiel in North Germany and at the mouth of the Somme and other spots on the coast of France.

Natural scalps are subject to extreme vicissitudes: an area of many acres may be destroyed by a local change of current producing a deposit of sand or shingle over the scalp, or by exposure to frost at low tide in winter, or by accumulation of decomposing vegetable matter. The chief localities of natural scalps on the British coast are Morecambe Bay in Lancashire and the flat eastern shores, especially that of the Wash of Lincoln, and similar shallow bays. These scalps are in some cases in the hands of private owners, but the English Government has not granted sufficiently definite rights to such individuals to enable them to protect their property from marauders, and to justify them in undertaking artificial cultivation.

The Sea Mussel is scarcely inferior in commercial value to the oyster. In 1873 the value of mussels exported from Antwerp alone to Paris to be used as human food was £280,000. In Britain their chief consumption is in the deep-sea line fishery, where they are held to be the most killing of all baits. Twenty-eight boats engaged in haddock-fishing at Eyemouth used between October 1882 and May 1883 920 tons of mussels (about 47 million individuals), costing nearly £1800 to the fishermen, about one-half of which sum was expended on the carriage of the mussels. It is quite impossible to calculate the number of tons of mussels annually used in this way by British fishermen, but it amounts to some hundreds of thousands, and the supplying of the market would offer a lucrative investment for capital did the Government grant definite proprietary rights over the fore-shore and sea-bottom to those ready to enter upon such enterprise. Many thousand tons of mussels are wastefully employed as manure by the farmers on lands adjoining scalp-producing coast, as in Lancashire and Norfolk, three half-pence a bushel being the price quoted in such cases. It is a curious fact, illustrative of the ignorant procedure and arbitrary fashions of fisher-folk, that on the Atlantic seaboard of the United States the Sea Mussel, Mytilus edulis, though common, is not used as bait nor as food. Instead, the Soft Clam, Mya arenaria, a Lamellibranch not used by English or Norwegian fishermen, though abundant on their shores, is employed as bait by the fishermen to the extent of 1⅛ million bushels per annum, valued at £120,000. At the mouth of the river Conway in North Wales the Sea Mussel is crushed in large quantities in order to extract pearls of an inferior quality which are occasionally found in these as in other Lamellibranch Molluscs (Gwyn Jeffreys).

Mytilus edulis is considered of fair size for eating when it is 2 inches in length, which size is attained in three years after the spat or young mussel has fixed itself. Under favourable circumstances it will grow much larger than this, specimens being recorded of 9 inches in length. It is very tolerant of fresh water, fattening best, as does the oyster, in water of density 1014 (the density of the water of the North Sea being 1026). Experiments made by removing mussels from salt water to brackish, and finally to quite fresh water show that it is even mote tolerant of fresh water than the oyster; of thirty mussels so transferred all were alive after fifteen days. Mytilus edulis is occasionally poisonous, owing to conditions not satisfactorily determined.

The fresh-water Mussels, Anodon cygneus, Unio pictorum, and TJnio margaritiferus belong to the order Isomya of Lamellibranch Molluscs, in which the anterior and posterior adductor muscles are equally developed. An account of the anatomy of Anodon is given in the article Mollusca. Unio differs in no important point from Anodon in internal structure. The family Unionacea, to which these genera belong, is of world-wide distribution, and its species occur only in ponds and rivers. A vast number of species arranged in several genera and sub-genera have been distinguished, but in the British Islands the three species above named are the only claimants to the title of “fresh-water mussel.”

Anodon cygneus, the Pond Mussel or Swan Mussel, appears to be entirely without economic importance. Unio pictorum, the common Biver Mussel (Thames), appears to owe its name to the fact that the shells were used at one time for holding water-colour paints as now shells of this species and of the Sea Mussel are used for holding gold and silver paint sold by artists’ colourmen, but it has no other economic value. Unio margaritiferas, the Pearl Mussel, was at one time of considerable importance as a source of pearls, and the pearl mussel fishery is to this day carried on under peculiar state regulations in Sweden and Saxony, and other parts of the Continent. In Scotland and Ireland the pearl mussel fishery was also of importance, but has altogether dwindled into insignificance since the opening up of commercial intercourse with the East and with the islands of the Pacific Ocean, whence finer and more abundant pearls than those of Unio margaritiferus arè derived.

In the last forty years of the last century pearls were exported from the Scotch fisheries to Paris to the value of £100,000; round pearls, the size of a pea, perfect in every respect, were worth £3 or £4. The Pearl Mussel is still used as bait in the Aberdeen cod fishery.

For an account of the anatomy of Mytilus edulis the reader is referred to the treatise by Sabatier on that subject (Paris, 1875). Its development from the egg has not been fully studied, but some very important facts as to the structure of the free-swimming young or spat are to be found in the memoir by Lacaze Duthiers, Annules des Sciences Naturelles, 1856. The essayby Mr Charles Harding on Molluscs used for Food or Bait, published by the committee of the London International Fisheries Exhibition, 1883, may be consulted as to the economic questions connected with the Sea Mussel. (E. R. I..)

In 1833 Musset published the volume called Un Spectacle dans un Fauteuil. One of the most striking pieces in this— Namouna— was written at the publisher’s request to fill up some empty space; and this fact is noteworthy when taken in conjunction with the horror which Musset afterwards so often expressed of doing anything like writing “to order,”—of writing, indeed, in any way or at any moment except when the inspiration or the fancy happened to seize him. The success of the volume seemed to be small in comparison with that of his Contes d ’ Espagne, but it led indirectly to Musset’s being engaged as a contributor to the Revue des Deux Mandes. In this he published, in April 1833, André del Sarto, and he followed this six weeks later with Les Caprices de Marianne. This play, which now ranks as one of the classical pieces in the repertory of the Théâtre Français, is a fine illustration of the method above referred to, a method of which Musset gave something like a definite explication five years later. This explication was also published in the Revue des Deux Mondes, and it set forth that the war between the classical and the romantic schools could never end in a definite victory for either school, nor was it desirable that it should so end. “It was time,” Musset said, “for a third school which should unite the merits of each.” And in Les Caprices de Marianne these merits are most curiously and happily combined. It so happens that, as the piece is generally given on the stage, with the omission of one change of scene, the classical unities are almost exactly preserved, while the whole play is impregnated with romanticism in the best sense of the word. It has perhaps more of the Shakespearean quality—the quality of artfully mingling the terrible, the grotesque, and the high comedy tones—which exists more or less in all Musset’s longer and more serious plays than is found in any other of these. In Claudio, the husband, the terrible and the grotesque are strangely and powerfully allied; Tibia, his serving-man, is grotesque with a touch of grimness caught from his master; Octave and Célio represent the two elements which were always warring in Musset’s own heart—one is the careless half-cynical man of the world and the other the wholly tender romantic lover; Marianne is that type of the highest comedy to which events lend a touch of tragedy, while in Hermia, Célio’s mother, is the very poetry of maternal love. The piece is called* a comedy, and it owes this title to its extraordinary brilliance of dialogue, truth of characterization, and swiftness in action, under which there is ever latent a sense of impending fate. Many of the qualities indicated are found in others of Musset’s dramatic works, and notably in On ne badine pas avec l' Amour, where the skill in insensibly preparing his hearers or readers through a succession of dazzling comedy scenes for the swift destruction of the end is very marked. But Les Caprices de Marianne is perhaps for this particular purpose of illustration the most compact and most typical of all. One other point in Musset’s method may be noted in connexion with this play. Paul de Musset asked him where he had ever met a Marianne. He answered, “Everywhere and nowhere; she is not a woman, she is woman.” The appearance of Les Caprices de Marianne in the Revue was followed by that of Rolla, a marked symptom of the “maladie du siècle.” Then came the unfortunate journey which Musset made to Italy with George Sand. It is well known that the rupture of what was for a time a most passionate attachment had a disastrous effect upon Musset, and brought out the weakest side of his moral character. He was at first absolutely and completely struck down by the blow. But it was not so well known until Paul de Musset pointed it out that the passion expressed in the Nuit de Décembre, written about twelve months after the journey to Italy, referred not to George Sand but to another and quite a different woman. The story of the Italian journey and its results are told under the guise of fiction from two points of view in the two volumes called respectively Elle et Lui and Lui et Elle. During Musset’s absence in Italy Fantasio was published in the Revue, and not long after his return On ne badine pas avec Γ Amour appeared in the same way. In 1835 he produced Lucie, La Nuit de Mai, La Quenouille de Barberine, Le Chandelier, La Loi sur la Presse, La Nuit de Décembre, and La Confession d'un Enfant du Siècle. The last-named work, a prose work, is exceptionally interesting as exhibiting the poet’s frame of mind at the time, and the approach to a revulsion from the Bonapartist ideas amid which he had been brought up in his childhood. To the supreme power of Napoleon he in this work attributed that moral sickness of the time which he described. “One man,” he wrote, “absorbed the whole life of Europe; the rest of the human race struggled to fill their lungs with the air that he had breathed.” When the emperor fell, “a ruined world was a resting-place for a generation weighted with care.” The Confession is further important, apart from its high literary merit, as exhibiting in many passages the poet’s tendency to shun or wildly protest against all that is disagreeable or difficult in human life— a tendency to which, however, much of his finest work was due. In 1836 appeared, amongst other things, Il ne faut jurer de Rien, a comedy which holds, and is likely long to hold, the stage of the Théâtre Français, and the beginning of the brilliant letters of Dupuis and Cotonet on romanticism. Il ne faut jurer de Rien is as typical of hi§ comedy work as is Les Caprices de Marianne of the work in which a terrible fatality underlies the brilliant dialogue and light keen characterization. In 1839 were published the Caprice (which afterwards found its way to the Paris stage through, in the first instance, the accident of Madame Allan the actress hearing of it in a Russian translation) and some of the Nouvelles. In 1839 he began a romance called Le Poète Déchu, of which the existing fragments are full of passion and insight. In 1840 he passed through a period of feeling that the public did not recognize his genius—as, indeed, they did not—and wrote a very short but very striking series of reflexions headed with the words “À trente Ans,” which Paul de Musset published in his Life. In 1841 there came out in the Revue de Paris Musset’s Le Rhin Allemand, an answer to Becker’s poem which appeared in the Revue des Deux Mondes. This fine war-song made a great deal of noise, and brought to the poet quantities of challenges from German officers. Between this date and 1845 he wrote comparatively little. In the last-named year the charming “proverbe” Il faut qu'une Porte soit ouverte ou fermée appeared. In 1847 Un Caprice was produced at the Théâtre Français, and the employment in it of such a word as “rebonsoir” shocked some of the old guard of the old school. In 1848 II ne faut jurer de Rien was played at the Théâtre Français, and the Chandelier at the Théâtre Historique. Between this date and 1851 Bettine was produced on the stage and Carmosine written; and between this time and the date of his death, from an affection of the heart, in May 1857, the poet produced no large work of importance.

Alfred de Musset now holds the rank which Sainte-Beuve first accorded, then denied, and then again accorded to him as a poet of the first rank. He had genius, though not genius of that strongest kind which its possessor can always keep in check. His own character worked both for and against his success as a writer. His very weakness and his own consciousness of it produced such beautiful work as, to take one instance, the Nuit d'Octobre, but it too often prevented him, from one cause or another, from producing any work at all. His Nouvelles are extraordinarily brilliant; his poems are charged with passion, fancy, and fine satiric power; in his plays he hit upon a method of his own, in which no one has dared or availed to follow him with any closeness. He was one of the first, most original, and in the end most successful of the first-rate writers included in the phrase “the 1830 period.” The wildness of his life, though it cannot be denied, has probably been exaggerated; and it has lately been suggested by Μ. Arsène Houssaye that the symptoms of the heart disease which caused his death may sometimes have been mistaken for the symptoms of intoxication. His brother Paul de Musset has given in his Biographie a striking testimony to the finer side of his character. In the later years of his life Musset was elected, not without some difficulty, a member of the French Academy. Besides the works above referred to, the Nouvelles et Contes and the Oeuvres Posthumes, in which there is much of interest concerning the great tragic actress Rachel, should be specially mentioned. Musset has had no successor in France either as a poet or as a dramatist. (W. H. P. )