be impracticable here to go into any dium. But we have now to observe oscillations by which the actual molethat the molecule itself is by no means cules are animated. to be regarded as a simple rigid parti- No doubt it is difficult to realize that cle; indeed, if it were so, it is certain much can be learned with regard to the that we should receive no heat at all performances that actually go on in the from the sun. We have the best rea- internal parts of a molecule, especially sons for believing that the molecule when it is remembered that each moleof matter, so far from resembling a cule in its entirety is so extremely simple rigid particle, is an elaborate minute as to be entirely beyond the structure, whose parts are in some reach of our organs of sense. It is, degree capable of independent move- nevertheless, impossible to doubt that ment. It will not, indeed, be necessary the statements just made correspond to for us to adopt the splendid hypothesis the véritable facts of nature. It would of Lord Kelvin, which supposes that molecules of matter are merely vortex rings in that perfect fluid, the ether. It seems difficult to doubt that this doctrine represents the facts, but if any one should reject it, then I have only to say that its assumption is not required for our present argument. All that is necessary for us is to regard each molecule as somewhat resembling an elastic structure made of parts which can quiver like springs, and so arranged as to be susceptible of many different modes of vibration. We are to suppose that each molecule, in addition to the energy which it possesses in virtue of its movement of translation as a whole, has also a store of energy corresponding to the oscillations of its electric springs. We can, in fact, in some cases determine the ratio which exists between the amount of energy which is, on the average, possessed by molecules in consequence of their velocities of translation, and the amount of energy which they possess in consequence of the vibrations by which their several parts are animated. It is these internal molecular vibrations which are of essential importance in our present inquiry. It is believed that the radiation of light or of heat, generally takes rise in the impulses given to ether by the internal molecular vibrations. Do we not know that the essential characteristic of those ethereal movements which correspond to radi-purpose of studying the particular charant light and heat is that they have the nature of oscillations? Such could not be imparted by mere rectilinear movements of the molecules as a whole. They must be due to those internal At the ordinary temperature of the air hydrogen is, of course, invisible; this means that the vibrations in the interior of the molecules are not sufficiently vehement to impart pulses to the ether with the energy that would be required to produce visual effects. Now, let us suppose that the hydrogen is heated. The effect of heating is to impart additional speed to the molecules of the gas, and consequently when the molecules happen to come together their encounter is more violent. The effect of such an occurrence on one of these little elastic bodies is to set it quivering with greater vehemence in those particular modes of vibration for which it is tuned. If the temperature of the gas has been raised sufficiently high, as it can be by the aid of electricity, then the internal energy acquired by the molecules, in consequence of the increased vehemence of their collisions, has become so great that they are able to impart pulses to the ether with sufficient intensity to affect our nerves of vision; thereupon we declare that the hydrogen is now so hot as to have become luminous. Suppose we employ a spectroscope for the acter of the light which the glowing a particular period of vibration of the have hitherto been engaged. In conether, and hence we see that the light sequence of the vast mass of the sun emitted by the hydrogen does not the gravitation with which it draws all consist of vibrations of all periods bodies towards it is very much greater indiscriminately, but only of certain than the gravitation on the surface of particular waves which are in unison the earth. On our globe we know that with the oscillations to which the in- the effect of gravitation is to impart to ternal parts of the molecule of hydro- any body near the surface velocity gen are adapted. Had we examined directed towards the earth's centre at the spectrum of some other gas in a the rate of thirty-two feet per second. state of incandescence we should have The sun is more than three hundred found a wholly different system of thousand times as massive as the earth; lines from those pertaining to hydro- we cannot, however, assert that the gen. This demonstrates that the mole- gravitation is increased in the same cules of one gas differ essentially from proportion, because, on account of the those of another in respect to the char- vast size of the sun, a particle at its acter of the internal vibrations which surface is more than a hundred times they are adapted to perform. The ex- farther away from the solar centre than traordinary activity of the movements a body on the surface of the earth is which take place within the molecules from the terrestrial centre. It can, may be appreciated from the following however, be shown that, taking these facts. We know that the wave corre- various matters into account, the actual sponding to one of the hydrogen lines intensity of gravitation at the solar has a length of about the forty-thou- surface is sufficient to tend to impart sandth of an inch; we also know that to all objects an increase of velocity in a single second of time light travels towards the sun's centre at the rate of over a space of a hundred and eighty-four hundred and fifty-seven feet per six thousand miles; a simple calcula- second. This would apply not only tion will, therefore, assure us that to a meteorite, or other considerable certain vibrations in the molecules of mass, which is falling into the sun; it hydrogen corresponding to this partic- would be equally true of an object as ular undulation must take place with small as a molecule. Every one of the such an extraordinary frequency that myriads of gaseous molecules in the about four hundred and sixty millions outer regions of the solar atmosphere of millions of them are performed in must be constantly acted upon by this each second of time. attractive force, which tends in the Provided with these conceptions we course of each second to add to them a shall now, I think, be able to see with- downward velocity at that rate per secout difficulty how it is that the sun's ond which has already been stated. heat is sustained. We may, for our is quite true that to a great extent the present purpose, think of the great effect of this attraction is masked by luminary as a mass of glowing gas. It counteracting tendencies. In particuis quite true that the physical condition |lar we may mention that, inasmuch as of the matter in the interior of the the density of the solar atmosphere tremendous globe can hardly be that increases as the sun's centre is apwhich we ordinarily consider as gase-proached, the flying molecule generally ous. But this need not affect our argu- finds itself more obstructed by encounment. It is undoubtedly true that ters with other molecules when it is those proportions of the solar atmo- descending than when it is ascending. sphere from which the light and heat We may here contrast the condition of are mainly dispensed are gaseous in the atmosphere on the earth with the their character, or, at all events, come condition of the solar atmosphere. sufficiently near to matter in the gase- Each molecule in our air, being acted ous state to permit the application of upon by terrestrial gravitation, has the line of argument with which we thereby a tendency to fall downwards It with a velocity continually increasing | to use for the purpose of sustaining its at the rate of thirty-two feet per sec- radiating capacity. Owing to the inond. As, however, the terrestrial at- tense heat which prevails in the photomosphere has long since reached a sphere, the molecules must there be stable condition, in which it undergoes in very rapid movement; their mutual no further contraction, the effect of encounters must be of the utmost vegravitation in adding velocity to the hemence, and their internal vibrations, molecules is so completely masked by which are the consequences of the the counteracting tendencies that, on shocks in the encounters, must be corthe whole, there is no continual in-respondingly energetic. It is, as we crease of molecular velocities down-have seen, these internal molecular wards due to gravitation. Were such vibrations which set the ether in moan increase at present going on, we tion, and thus dispense solar heat and should necessarily find that the terres- light far and wide through the unitrial atmosphere was decreasing in verse. But this the molecules can only volume, and ever becoming more con- do at the expense of the energy which densed in its lower strata. It is, how- they possess in virtue of their internal ever, well known that no such changes vibrations. Unless, therefore, the inas are here implied are taking place. ternal molecular energy were to be in The essential difference between the some way recuperated from time to earth and the sun, so far as the matter time, the radiating power must necesnow before us is concerned, is to be sarily flag. It is now plain that the found in the fact that, as the sun has necessary recuperation takes place in not yet passed into the form of a rigid the successive encounters. A molecule body, it is still contracting at a rate whose internal energy of vibration is very much greater than that at which becoming exhausted by the effort of a body grown so cold as the earth draws setting the ether into vibration presits particles closer together. The mole-ently impinges against some cules in the solar photosphere accord-molecule, and in consequence of the ingly yield to a certain extent to the blow is again set into active vibration gravitation which constantly seeks to which permits it to carry on the work draw them down. The counteracting of radiation anew, until its declining tendencies cannot in the sun, as they energies have again to be sustained by do in the earth, mask the direct and some similar addition arising from a obvious effect of gravitation. The fresh collision. Of course, we know consequence is that the intense attrac- that the internal molecular energy thus tion which is capable of adding velocity acquired cannot be created out of nothto the molecules at the phenomenal ing. If the molecule receives such acrate of four hundred and fifty-seven cessions of internal energy, it must be feet per second is permitted to accom- at the expense of the energy which is plish something, and thus increase the elsewhere. Obviously the only posaverage speeds with which the mole-sible source of such energy must be cules hurry along. To express the found in the movement of the molematter a little more accurately, we should say that the downward velocity imparted by gravitation, being compounded with the velocities otherwise possessed by the molecules, tends, on the whole, to increase the rate at which they move. We shall now be able to discern what actually takes place as the sun contracts by dispersing heat, and in consequence of its decline in bulk finds a store of energy liberated which it is permitted other cule as a whole, that is to say, in the velocity of translation with which it rushes about among the other molecules. Thus we see that the immediate effect of expenditure of heat or light by radiation is to diminish the internal energies of the molecules. These energies are restored by the transference of energy obtained from the general velocities of the molecules regarded as moving projectiles. It follows that the velocities of the several particles must on the whole tend to decline; in other here following attributes eternal vigor words, that the temperature tends to to the great luminary. It will be noted fall. What we have to discover is the that it is of the essence of the arguagent which at present prevents the ment that the contraction is still in solar temperature from falling. We progress. If the contraction were to want, therefore, to ascertain the means cease, then the restitution of velocity by which the molecular velocities are by gravitation would cease also, and preserved at the same average value, the speedy dispersal of the existing notwithstanding that there is a con- heat by radiation would presently prostant tendency for these velocities to duce bankruptcy in the supply of sunabate in consequence of the losses of beams. Indeed, such bankruptcy must light and heat by radiation. We have arrive in due time, when, after certain already explained how the gravitation millions of years, the sun has so far of the sun constantly tends to impart contracted that it ceases to be a gaseous additional downward velocity to the mass. The vast accumulated store of molecules in its atmosphere. This is energy which is now being drawn upon, precisely the action which we now to supply the current radiation, will require. The contraction of the sun then yield such supplies no longer. tends to an augmentation of the mo- Once this state has been reached, a lecular velocities, and this augmenta- few thousand years more must witness tion just goes to supply the loss of the extinction of the sun altogether as velocities which is the consequence of a source of light, and the great orb, at the radiation. A complete explanation present our splendid luminary, will of the maintenance of the sun's heat is then pass over into the ranks of the thus afforded. Observation, no doubt, innumerable host of bodies which were seems to show that the capacity for once suns, but are now suns no longer. radiation is at present sensibly conROBERT BALL. stant, and this being so, we see that the gain of molecular velocities from gravitation and their losses from radiation are at present just adapted to neutralize each other. Nothing, however, that has as yet been said demonstrates that the efficiency of the sun for radiating light and heat must always be preserved exactly at its present value. It is quite possible that if we had the means of studying the sun heat for a hundred thousand years, we might find that the capacity for radiation was slightly decreasing, or, it may be, that it would be slightly increasing, for it is at least conceivable that the gain of molecular velocity due to gravitation may, on the whole, exceed the loss due to the dispersal of energy by radiation. On the other hand, it is, of course, possible that the acquisition of velocity by gravitation, though nearly sufficient to countervail the expenditure by radiation, may not be quite enough, in which case the sun's temperature would be slowly declining. From Blackwood's Magazine. Or don't, 'ould be presumin'; I. THE HEIRESS. ,, MRS. FARQUHAR was thirty years younger than her husband. The fact, originally a pleasure to him, became afterwards an offence, and he quarrelled with her for no better reason. At least, so said Mr. Nevill, his cousin; and so said every one at all acquainted with the harmless lady. Old John Farquhar died at seventy-six, and left his widow not one penny of money. And her son, young John as good a boy as ever was seen, a smart young soldier, who had never offended his father till a year ago, and then It must not, however, be supposed only by over-warm intercession for his that the argument which we have been mother-found himself cut down to What, my love, is the matter ?" inquired her father. a pittance of two hundred a year. Jessica threw down the pen and be "I don't want to marry John Farquhar," sobbed Jessica. Mr. Nevill bit his lip impatiently and demanded reasons, and Jessica, found it supremely hard to make them intelligible. Of course gentle Mrs. Farquhar cried herself ill, and said it was all her fault; and of course young John was aghast, and believed himself on the workhouse "I don't want to marry till I'm at threshold. But Mr. Nevill took the least twenty-eight papa. I shouldn't matter more to heart than did either, mind if I were an old maid. I want to and his very hair stood on end with go to Girton, papa; and to be-to be dismay; for he was an extremely high-cultured. I mean, I want to be supesouled gentleman, horrified to think a rior." member of his household should profit : "You must try to express yourself 66 Papa,' ," said Jessica, who till this moment had imprisoned her aspirations in her breast, and who, though she loved her father dearly, was not much in the habit of talking to him 66 рара, Lady Sterne was married at my age, and now she is so stout, and has so much to do, and she always seems so tired of her husband, and so tired of babies, and every one thinks her so stupid." by such monstrous injustice. Jessica more clearly," said Mr. Nevill. at this time was eighteen, pretty, and the apple of her father's eye; rather a clever little person, who, having left school, wanted now to go to college. But she did not understand money matters, and became, under the present circumstances, just a little annoying to her papa. For her remarks were so very perfunctory and childish; and one moment she was building with her wealth some extravagant castle in Spain, and the next clamoring to pack "You have not yet made your meanit all up in a parcel and send it off by ing clear, Jessica," said Mr. Nevill.. post to her cousin John. Clearly, how- "I should much rather be like dear ever, there was but one comfortable Miss Snow, who is always so nicely solution of the difficulty: the heiress dressed, and who reads. so much, and must marry John Farquhar, and so re-writes for the Sunday at Home, papa. store to him his inheritance. This I mean, what is the good of marrying project was the simultaneous invention at all?" cried Jessica. "And if ever of both Mr. Nevill and the widow. It I do get married, I want to marry a was propounded to John, who, after a whom. I esteem and little hesitation, and having no fancy Here Jessica colored. for the workhouse, agreed. Provision- Mr. Nevill explained that she was ally that is; in Jessica's interest he at full liberty to worship John Farinserted in the treaty a saving clause.quhar, but that she must not keep him "If," he wrote, "your daughter is ten years waiting for his money; and perfectly willing; at present, and when then he advised her to go ou with her we shall have become acquainted.” letter. "Very proper," commented Mr. Nevill; "could not be more proper. Every word John says is admirable. You are to be congratulated on your husband, Jessica. Sit down, my dear, and write him a cordial response."? person ship." wor Jessica tried again. "But John Farquhar seems quite an ordinary person, papa, and I don't suppose. I shall find it the least possible to esteem and to worship him." "Then you had better love him," said Mr. Nevill dryly-"that will do as well." “Papa, I Jessica grew very pink. |