Licence: Public Domain Mark
Credit: The problems of "psychic research". Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![SATURN’S RINGS. 75 tliey may move through each other ir- regularly, In the first case the destruc- tion of the system will be very slow; in the second case it will be more rapid, but there may be a tendency toward an ar- rangement in narrow rings, which may retard the process. “We are not able to ascertain bv obsei*- «/ vation tlie constitution of the two outer di- visions of the system of rings, but the inner ring is certainly transparent, for the limb (t. c.,edge) of Saturn has been observed through it. It is also certain that though the space occupied by tl>e ring is transpar- ent, it is not through the material i)articles of it that Saturn was seen, for his limb was observed without distortion, which shows that there was no refraction, and therefore that the rays did not passthrough a medium at all, but between the solid or liquid particles of which the ring is composed. Here, then, we have an o])- tical argument in favor of the theory of/ independent particles as the material ol’ the rings. The two outer rings may be of the same nature, but not so exceeding- ly rare that a ray of light can pass through their whole thickness without encounter- ing one of the particles.” It lias thus been shown by several lines of investigation that Saturn’s ripgs consist of independent meteorites, moving, each in its orbit, about the planet, and this con- clusion may be safely accepted as correct. But every field of thought is now seething with the evolutionary ferment, and as we cannot rest .satisfied with any conclusion as a finality', Ave here merely find ourselves at the starting-point of new .speculations. What, then, is the history of the.se rings, and what their future fate? They are clear]} intimately related to the ])lanet, and their history would be com])lete if we could with the mind's eye Avatch their birth from the planet and follow their sidxsequent changes. Now although the details of such a history are obscure, yet at least a shadowy outline of it may be confidently accepted as known. In the remote past all the matter Avhich now forms the Saturnian system of ])lanet, satellites, and rings Avas far more dif- fu.sed than at present. Thei’e Avas ])roba- bly a nucleus of denser matter round Avhich .slowly revolved a mass of rarefied gases and meteorites. The central por- tion AA-as iiitensely hot, Avith heat derived by condensation fi-om a .state of still great- er disper.sion. Voi.. I.XXIX.—No. 4C9.-r As this nebula cooled it contracted, and therefore revolved more quickly. If you watch the AA^ater emptying itself from a common AA’a.sh-hand basin Avhen the plug at the bottom is removed, you Avill see an example of such quickened rotation. When the basin is full, the water is com- monly revolA’ing .slowly in one or the other dii'ection, but as the level falls and the AA-ater approaches the hole, it spins more quickly, and the last drops are seen to whirl round Avith violence. The revoWing nebula is flattened at the ])oles like -Un orange, and the amount of flattening increa.ses as it contracts and spins quicker. At a certain stage it can no longer subsist in a continuous masS; and an annular ])ortion is detached from the/equator, leaving the centml ball to coiitinue its conti’action. We are pretty .safe in saying that the rings of Saturn took their origin in some such mode as this. But it cannot be main- tained that Ave understand it all, for Ave haAe not more than a vague picture of the primitive nebula, and the mode in Avhich the matter aggregated itself into a ring and detached itself is obscure, M. Roche has done perhaps more than any one else to impart mathematical precision to these ideas, but even he has not been Avholly succes.sful. This theory, commonly called the neb- ular hypothesis, Avas advanced indepen- dently both by the philosopher Kant and by Laplace. Various modifications have been suggested by others, but the theory, in Avhatever form, is replete Avith difficul- ties, and must at ])resent be only regarded ns an approximation to the truth.* If the past liislory of the ring is not Avholly clear, it is at least more ascertain- able than its future development. It is nearly certain that the ring now presents a markedly different appearance from that Avhich AAas seen by its discoverers. Indeed the only doubt lies in the uncertainty as to the amount of allowance which must be made for differences of ohservers and of instruments. Huygens described the interval between the bright ring and the planet as rather exceeding the width of the ring, but Ave need only look at Fig. 1 or 2 to see that this is now flagrantly in- correct. It is improbable that Huygens * I liave recently presented .i paper to tlie Royal Society of London (.Vovember, 1888), in wliieli I have tried to throw light on the mechanical pro- cesses involved in the nebular liypothc.=is.](https://iiif.wellcomecollection.org/image/b22468006_0004.jp2/full/800%2C/0/default.jpg)
