quick as a rat-trap, and the poor bird instantly became a prisoner to die (or possibly get drowned as the tide rose) in his prison.

"A story is told of a nigger in America who was caught in a somewhat similar manner. The nigger put his tongue between the shells

it.

of a half-opened oyster to suck out the juice, and the oyster caught him tightly by the tongue. Sambo, when released, was chaffed about Why, the oyster could not have hurt you,' said his friend; 'he has no teeth.' 'No,' said Sambo, 'he 'ave no teeth, but by Gorry he have dam hard gums

999

In the late report on "The Sea-Fisheries " Mr. Buckland published a large mass of information in regard to mussels. In the course of this he says:

"Mussels have a great number of enemies, the chief of which are

VOL. XVII.-8

RAIL CAUGHT BY OYSTER.

five-fingers, or star-fish, and whelk-tingles. It is most interesting to watch the five-fingers eating the mussels. The whelk-tingles, or white buckies, as they are called at Montrose, will clear off in a few hours a large acreage of mussels. The proprietors, therefore, employ women and children to pick them off at low tide. Not only are mussels largely used as bait, but they are a favorite food of the poor, and are sold in large quantities in the streets of the large towns of England-Manchester, Liverpool, Birmingham, etc. They are, in fact, the poor man's oyster.' So much, indeed, are mussels used as food, that a proposition was more than once seriously made to us by the fishermen that it should be illegal to use mussels for human food. As regards their value as food, I have made the following calculation: There are on the average thirty-nine mussels to the pound, equal to 87,360 mussels in a ton. These cost first hand £1 5s. per ton; the cost to the retailers is £3 6s. 8d. per ton. In March, 1876, a large number of crows were observed eating mussels (query, fresh-water) in the Norfolk Broads. There are large quantities of mussels in many of the broads and rivers, especially in South Walsham Broad, and also, I believe, in Hoveton Broad, Ormesby Broad, and Fritton Water. At the present time I believe no use whatever is made of them; it is as well to see if these mussels can not be cultivated and used for bait.”—Land and Water.

HOW INSECTS DIRECT THEIR FLIGHT.*

By M. J. DE BELLESME.

THE works of M. Marey have nicely determined the difference be

tween the manner in which birds and insects fly. The bird can change at will the angle of vibration of his wings, and therefore these organs serve to steer his flight. The insect is deprived of this power, because the angle of vibration, as a rule, is invariable in each species, the flying-muscles not being in the wings, but in that part of the thorax which supports the wings.

Knowing these facts, I concluded that if the wing of the insect be merely a motor apparatus, the steering function must be sought for elsewhere; and, from numerous experiments made upon insects of every order, I am convinced that the steering power depends upon the position of the head and thorax, this, in its turn, depending upon the respective positions of the center of gravity and the axis of suspension (l'axe de sustention). Both these elements are sometimes movable, but more often it is the center of gravity which changes.

*From a paper read before the Paris Academy of Sciences, and published in "Comptes Rendus." Translated by M. Howland.

There are a few insects in which the motor and steering functions are united, the flying-muscles being attached to the wings. These insects fly gracefully, like birds; still, the abdomen is very long, flexible, and greatly augments the ease and variety of motion; this is specially apparent in the Agrions-the dragon-fly, for example. It is probable that the Lepidoptera (butterflies, moths) should be ranged in the same category, for the movement of their wings is something like that of birds; the anatomy of their thoracic muscles, however, has not yet been completely analyzed.

In the Hymenoptera (bees, wasps, etc.) are found the first indications of separate functions of translation and direction. The wings, having acquired a very perfect automatism by which the axis of suspension has become permanently fixed, are solely devoted to the function of movement. The abdomen has become pediculated and exceedingly mobile. As it bends up or straightens out, the center of gravity is carried forward or backward. The Cynips (gall-flies, etc.) and Ichneumonides (insects that prey upon the eggs of other insects) offer extreme examples. If the abdomen be prevented from moving, the animal can still fly, but can not direct its course. Moreover, the posterior legs of these insects are long, as in the Polistes and Megachiles, and this also aids in displacing the center of gravity.

In the Orthoptera (crickets, grasshoppers, etc.) the abdomen is but slightly movable, and the steering power is almost wholly in the hindfeet; but, as these are already differentiated for an equally important function, that of jumping, they lend themselves with a bad grace to the former function, and so the hopping insects fly very badly.

Thus far we have seen the two pairs of wings devoted to the motor function. We come now to a class of insects in which the functional adaptation is not secured through organs performing other functions and lending themselves to extra duties, but where the adaptation is secured through its own proper organs-one of the pairs of wings, indeed, which, diverted from the motor function, has become a steering apparatus.

In the group of Coleopters (beetles), only one pair of wings, the posterior, serve to sustain the insect; the surface of support, therefore, is considerably diminished, and the flight is heavy or clumsy. But this disadvantage is compensated by the greater extent of surface afforded by the non-modified pair. This surface, indeed, is so great that the insect is obliged to fold it up during rest. The abdomen of the Coleoptera is stiffly fixed to the thorax, and consequently is but slightly movable; but this quality is unnecessary, since a special organ, the elytrum (wing-case), has power to displace the center of gravity. Raised up over the thorax during flight, the elytrum forms a little swaying mass above the center of gravity, and the slightest motion of this mass affects the balance of the insect. Remove the wing-cases, and the insect still flies, but has no power to direct its motion, which

is upward, downward, or horizontal, according to the position of the center of gravity at the moment of the experiment. M. Plateau has clearly demonstrated that the normal position of this point varies with each species.

One very small group, the Cetoniada, fly with the wing-cases down-an interesting fact, for in this instance they act upon the axis of suspension, and effect a step toward the state of complete differentiation which we find in the following group.

In the Diptera (mosquitoes, flies, etc.) the steering faculty reaches its highest development. The second pair of wings is transformed into organs having the special function of steering, the balancers or poisers; and these insects have accordingly a remarkable perfection of movement. A single pair of wings does all the flying, and, as they are not large, the diminution of the supporting surface is compensated by greater rapidity of vibration. I have proved by experiment that the balancers act by displacing the axis of suspension. Suppress the balancers, and the flight becomes fatally downward, because the normal and invariable position of the center of gravity is in front of the axis of suspension; the animal, therefore, can not modify his movement in any way, the abdomen being but slightly movable, and the balancers cut off. If, now, we come to his relief and attach a tiny weight to his abdomen, just sufficient to carry the center of gravity back to its normal place, we restore to the insect the power to perform all his aërial evolutions.

A

SKETCH OF JAMES CLERK MAXWELL.

MONG the present generation of English physicists none have attained to greater eminence, or have made more valuable additions to this department of science, than the late Professor Maxwell. The splendid promise that his accomplished work gave of future work makes his death, at the early age of forty-nine, at the height of his powers, an irreparable loss to science. An accomplished mathematician, an unexcelled experimenter, he was peculiarly fitted to carry on those delicate researches in the domain of molecular physics by which he made it his own, and in which he was without a rival. Possessed of a vivid imagination, he had that power of holding it well under control, and making it subservient to the conditions of scientific investigation, that belongs only to the highest types of mind, and which is essential to the best and most valuable work in science. Though possessed of the power of direct and lucid exposition, he was never what is termed a popular lecturer. The subjects he considered, and his con

densed form of presenting them, debarred any, save those whose knowledge was sufficiently extended, from following him in his exposition. But, by the students who enjoyed the privilege of attending his lectures, he was regarded as a teacher of the greatest value, though at times somewhat difficult to follow. Of a kindly and genial disposition, Professor Maxwell secured the affectionate regard of those with whom he came in contact, and to many his death comes as the double loss of a companion in work and of a valued friend.

Professor Maxwell was born in the year 1831, being the only son of John Clerk Maxwell, Esq., of Middlebie, Dumfriesshire, Scotland. When eight years old his mother died, and his father thereafter lived a retired life on his estate, devoting himself to the education of his son and the care of his property. He received his early education at the Edinburgh Academy, and after leaving there entered the University of Edinburgh. In 1850 he went to Cambridge, from which he was graduated in 1854, as second wrangler. In the following year he became a Fellow of Trinity College, and a year later accepted the position of Professor of Natural Philosophy in Marischal College, Aberdeen, which he held until the fusion of this and King's College. He succeeded Professor Goodeve as Professor of Natural Philosophy and Astronomy in King's College in 1860, and remained there until the death of his father in 1865, when he retired to his estate in Scotland. None of these positions had been entirely in accordance with his tastes, or such as to give full scope to his abilities. Such an opportunity as in every way suited him was opened to him in 1871, by the invitation of the University of Cambridge to the newly created chair of Experimental Physics, which he held until the time of his death. Shortly after his acceptance of the position, the Cavendish Laboratory, with a complete equipment of apparatus, was presented to the university by the Duke of Devonshire, and it is due to the superintendence of Professor Maxwell that this laboratory is so excellently adapted to its purpose.

During the winter of 1878 and 1879 Professor Maxwell's health failed him, and in the spring he betook himself to Scotland in the hope of regaining it. He was not improved by his trip, and he therefore returned to Cambridge, where under the treatment of Dr. Paget he grew better, and hopes were entertained of his recovery. The improvement, however, was not lasting, and he rapidly grew weaker until his death, on the 5th of November last.

Professor Maxwell commenced original work at an early age, and his contributions to the "Transactions" of societies and scientific periodicals have been voluminous. A mathematical paper "On the Description of Oval Curves, and those having a Plurality of Foci," was submitted by him to the Royal Society of Edinburgh, through Professor Forbes, before he was fifteen. While at the University of Edinburgh he contributed two elaborate papers to the Edinburgh Royal Society,