and pessimism are both of them plausible views, it seems almost futile to try to determine what thought or fact it is which makes for each man the transition from despair to faith. There are plenty of phenomena to lead anybody to any conclusion.

It is enough to give her own account of the means by which this change was effected; which means she believed to be divine grace, sent in answer to prolonged and earnest prayer :—

Je crois encore à ce que les chrétiens appellent la grâce. Qu'on nomme comme on voudra les transformations qui s'opèrent en nous quand nous appelons énergiquement le principe divin de l'infini au secours de notre faiblesse; que ce bienfait s'appelle secours ou assimilation; que notre aspiration s'appelle prière ou exaltation d'esprit, il est certain que l'âme se retrempe dans les élans religieux. Je l'ai toujours éprouvé d'une manière si évidente pour moi, que j'aurais mauvaise grâce à en matérialiser l'expression sous ma plume. Prier comme certains dévots pour demander au ciel la pluie ou le soleil, c'est-à-dire des pommes de terre et des écus, pour conjurer la grêle ou la foudre, la maladie ou la mort, c'est de l'idolâtrie pure; mais lui demander le courage, la sagesse, l'amour, c'est ne pas intervertir l'ordre de ses lois immuables, c'est puiser à un foyer qui ne nous attirerait pas sans cesse si, par sa nature, il n'était pas capable de nous réchauffer.

Through whatever agency, the change took place. For the rest of her long life George Sand was, not strictly a Christian, but one of those who must be ranged along with Christians in any reckoning of the spiritual forces of the world. For we know that the true controversy is no longer between those within and those without the walls. of any given church, but on a wider scale and involving profounder issues. It is a controversy between Spiritualism and Materialism, between those who base their life upon God and immortality, and those who deny or are indifferent to both. And the spiritual cause has the more need of champions now that a distinct moral superiority can no longer be claimed on either side. Perhaps the loftiest and most impressive strain-of ethical teaching which is to be heard in England now, comes from one who invokes no celestial assistance, and offers to virtue no ultimate recompense of reward. The Stoics are again among us; the stern disinterestedness of their counsels of perfection' is enchaining some of our noblest souls. But the moral elevation of any portion of mankind tends to the elevation of all. And although to those who rest tranquil in their belief in immortality this stoical view will appear extreme, one-sided, hopeless, impossible to man, it will yet teach them no longer to speak as if virtue were to be repaid with pleasures which it needs no virtue to enjoy. They will rather claim that a spirit of ceaseless aspiration shall be satisfied with a ceaseless progress; that virtue shall be rewarded by her own continuance, 'the wages of going on, and not to die.'

Few writers have dwelt on this prospect with a more sustained

and humble aspiration than George Sand. I quote one of number

less passages:—

Saintes promesses des cieux où l'on se retrouve et où l'on se reconnaît, vous n'êtes pas un vain rêve. Si nous ne devons pas aspirer à la béatitude des purs esprits du pays des chimères, si nous devons entrevoir toujours au-delà de cette vie un travail, un devoir, des épreuves et une organisation limitée dans ses facultés vis-à-vis de l'infini, du moins il nous est permis par la raison, et il nous est commandé par le cœur de compter sur une suite d'existences progressives en raison de nos bons désirs. Les saints de toutes les religions qui nous crient du fond de l'antiquité de nous dégager de la matière pour nous élever dans la hiérarchie céleste des esprits ne nous ont pas trompés quant au fond de la croyance admissible à la raison moderne. Nous pensons aujourd'hui que, si nous sommes immortels, c'est à la condition de revêtir sans cesse des organes nouveaux pour compléter notre être, qui n'a probablement pas le droit de devenir un pur esprit; mais nous pouvons regarder cette terre comme un lieu de passage et compter sur un réveil plus doux dans le berceau qui nous attend ailleurs. De mondes en mondes, nous pouvons, en nous dégageant de l'animalité qui combat ici-bas notre spiritualisme, nous rendre propres à revêtir un corps plus pur, plus approprié aux besoins de l'âme, moins combattu et moins entravé par les infirmités de la vie humaine telle que nous la subissons ici-bas.

With some such thoughts as these we should close our contemplation of the earthly career of a strong, a militant, an eager soul. To one who traces the victories of such a soul, in this dimness of her captivity, that which she hath done will seem but earnest of the things that she shall do;' we imagine her delivered from the bewildering senses, the importunate passions of the flesh, no longer 'tormented,' but satisfied, with the things of God; glad in those spiritual kinships and that inward calm towards which 'her continual longing has been her continual voice.'

FREDERIC W. H. MYERS.

VOL. I.-No. 2.

R.

THE RADIOMETER AND ITS LESSONS.

SOMEWHAT less than two years ago, the large assemblage of scientific men gathered at the soirée of the Royal Society was startled at the sight of a phenomenon which was altogether new and strange to the great majority of them. In the interior of a thin glass globe, about the size of a small orange, prolonged below into a cylindrical stem by which it was supported on a stand, Mr. Crookes presented to our view a horizontal cross of four slender arms radiating at right angles from a common centre; the extremity of each arm carried a thin disc about the size of a threepenny piece, black on one side and white on the other, the black sides all facing alike; while beneath the centre was a pointed steel pivot, resting on a cup that formed the summit of a rod fixed into the cylindrical stem,' on which the cross with its terminal discs was free to revolve horizontally-exactly after the fashion (in miniature) of Dr. Robinson's cup-anemometer for recording the velocity of wind. The globe, Mr. Crookes informed us, had been exhausted of air to the utmost degree attainable by the 'Sprengel pump' as improved by himself, and had been then hermetically sealed. Without any other perceptible agency than the general light of the apartment, the cross slowly rotated horizontally in the direction of the white sides of the discs. When a candle was brought within a foot or so of the globe, the rotation became much quicker. When the candle was approximated to within two or three inches of the globe, the cross spun rapidly round. And when a piece of magnesium wire was burned close to it, the rapidity of the rotation became so great that the discs could no longer be separately distinguished!

The effect was not perceptibly diminished by the interposition, between the globe and the candle or other source of light, of a glass trough containing a solution of alum, which, while transparent to light, stops a large part of the radiant heat which accompanies it. And what was yet more remarkable-if, while the cross was rotating rapidly under the influence of a candle within a short distance, the

In the Radiometer as now constructed, the arms radiate from an inverted cup, which rests upon the pointed pivot-an arrangement that is in many respects more convenient.

flame of a spirit-lamp was made to play over the surface of the globe, the rotation was checked in a very peculiar manner; the cross being, as it were, pulled up with a jerking action, much as when the swinging of a compass-needle is stopped by the attraction of a magnet brought near it. When, on the other hand, the spirit-lamp was withdrawn, the candle remaining where it was, the rotation commenced anew as the globe cooled.

It is scarcely surprising, then, that a general impression should have at once prevailed that a capital discovery had been made-that of the direct mechanical action of light; which, though not indicating the existence of a new force in nature, showed that the most universally diffused of all forces, next to gravitation, has a mode of action which was previously not merely unknown, but altogether unsuspected. And this impression was not confined to those who had only a general acquaintance with Physical Optics; for it was shared by the greatest masters of that department of science, who had followed the course of the experimental researches on which Mr. Crookes had been for some time engaged, and of which this discovery was the culmination.

The origin of these researches was rather singular. In the course of the weighings made by Mr. Crookes to determine the atomic weight of the new metal thallium, his discovery of which by spectrum analysis had acquired for him deserved distinction as a chemist, he noticed that when the balance was enclosed in a case, and the substance weighed was of a temperature higher than that of the surrounding air and apparatus, there was an interference with the due action of the balance, which seemed attributable to the currents set up in the air within the case by the inequality of its temperature. Experiments were then made to render the action more sensible, so as to discover and eliminate sources of error; and in the course of these it was discovered that when a small light body is delicately suspended in the most perfect vacuum that can be produced, it is repelled by radiant heat or light, although the same body suspended in the same vessel, from which the air has not been exhausted, seems attracted by the same radiant force. This can be demonstrated by suspending a bar of pith by a fibre of cocoon-silk within a glass globe, so as to constitute what is known as a 'balance of torsion,' and subjecting one end of this bar to the influence of heat. When the globe is full of air, the warmed end of the bar swings towards the source of heat; but when the globe has been thoroughly exhausted and hermetically sealed, the bar is made to swing away to the extent of 90°, by merely touching with the finger the part of the globe near one of its extremities; whilst, on the other hand, it follows a piece of ice as a suspended needle follows a magnet. These contrary effects are very strikingly shown when two similar globes, each having a pith-bar suspended in it, but the one full of air and the other exhausted, are placed side by

side; and a hot glass rod on the one hand, and a piece of ice on the other, are moved round each in succession. For the bar in the unexhausted globe behaves exactly with the heated rod as the bar in the exhausted globe does with the ice; and the bar in the unexhausted globe behaves with the ice exactly as the bar in the exhausted globe behaves with the heated rod. Again, when a candle is brought within about two inches of a well-exhausted globe, the pith-bar begins to oscillate backwards and forwards, its swing gradually increasing until its position is reversed; and when the 'dead centre' has been passed, it revolves continuously, until the torsion of the suspended fibre offers a sufficient resistance to prevent any further movement in the same direction. A contrary revolution then begins, which proceeds as far in the opposite direction; the alternating series of revolutions being kept up as long as the candle burns.

A still more sensitive apparatus of the like kind was afterwards devised by Mr. Crookes, in which two discs of pith were attached to the extremities of a very slender glass rod, and this was suspended horizontally by a fine fibre of spun glass; the whole being hermetically sealed within a glass vessel of suitable form, from which the air was removed as completely as possible. The advantage of suspending the beam by a glass fibre lies in its elasticity; which is so perfect, that, however much the fibre may have been twisted, the beam always returns accurately to zero when free to do so. And by drawing out the fibre to the requisite degree of fineness, this 'torsion-balance' may be made of any degree of sensitiveness that may be required; one which was used in Mr. Crookes's subsequent experiments being so delicate as to turn to the millionth of a grain.

From this form of apparatus, the transition was obvious to one in which the arms, instead of being suspended by a fibre, should rest on a point, so as to be free to rotate continuously in either direction; and thus originated the Radiometer,—the name given to it by Mr. Crookes being intended to express its action as a measurer of the mechanical power directly exerted by that Radiant Energy which had been previously known to manifest itself only under the forms of Light, Heat, and Actinism (or chemical agency). This was the sense in which its phenomena were brought under discussion at the ordinary meeting of the Royal Society next following the first exhibition of the radiometer; and so demonstrative did these seem to be of 'A Repulsion resulting from Radiation' (the title of Mr. Crookes's memoir), that no one of the eminent Physicists present on the occasion called his interpretation of them in question; Professor Stokes, in particular, confining himself to the statement that such mechanical action must lie outside the Undulatory Theory, which deals only with light as light-i.e. as producing visual phenomena. But it was noticed by several as anomalous, that the black should be the 'driving side of the discs, since it might have been anticipated that the