,,stellar ,,evolution ---------------------------------------- -------------------------------- ,,by ,,the ,,same ,,author4 ------- ,,climate ,,and ,,time ,,in ,,their ,,geological ,,relations3 ,a ,theory of ,secular ,changes of the ,earth's ,climate4 ,by ,,james ,,croll1 of ,h4 ,m4 ,geological ,survey of ,scotland4 ,with ,maps and ,illustrations4 #abmo4 ,cloth1 #b4ej4 ,,discussions ,,on ,,climate ,,and ,,cosmology4 ,by ,,james ,,croll1 ,,ll4,d41 ,f4,r4,s4 ,with ,chart4 #abmo4 ,cloth1 #b4jj4 ---------------------------------------- -------------------------------- ,,stellar ,,evolution ,,and ,,its ,,relations ,,to ,,geological ,,time ,,by ,,james ,,croll1 ,,ll4,d41 ,f4,r4,s4 ,,author ,,of #8,,climate ,,and ,,time1' #8,,climate ,,and ,,cosmology1' ,,etc4 ,,new ,,york ,d4 ,,appleton ,,and ,,company #ahhi ---------------------------------------- -------------------------------- ,authorized ,edition4 ---------------------------------------- -------------------------------- ,,preface4 ,illustration ,there are two1 and only two1 conceivable sources from which the prodigious amount of energy possessed by our sun and solar system can possibly have been derived4 ,not only are these two sources radically distinct in their essential nature1 but both are admitted to be real and not merely hypothetical sources of energy4 ,the one source is gravitation2 the other1 the source discussed in the present volume1 a source to which attention was directed some twenty years ago4 ,a most important distinction between these two sources is this3 the amount of energy available from the former can be accurately determined1 but such is not the case in regard to the latter4 ,we can tell with tolerable certainty the greatest amount of energy which gravitation could possibly have conferred on the sun and solar system2 but we have1 at present1 no means of assigning a limit to the possible amount which might have been derived from the other source4 ,it may have been equal to that which gravitation could afford1 or it may have been twofold1 fourfold1 or even tenfold that amount4 ,we have evidently in this case a means of determining which of the two sources will ultimately have to be adopted as the source to which the energy of our solar system must be referred4 ,for if it can be proved from the admitted facts of geology1 biology1 and other sciences1 that the amount of energy in the form of heat which has been radiated into space by the sun during geological time is far greater than the amount which could possibly have been derived from gravitation1 this will undoubtedly show that gravitation cannot account for the energy originally possessed by our system4 ,the ,first ,part of the volume is devoted to the consideration of what ,i believe to be the probable origin of meteorites1 comets1 and nebul1 and of the real source from which our sun derived his energy4 ,the facts which support the theory here advocated1 together with the light which that theory appears to cast upon those facts1 are next considered2 and it will be found1 ,i think1 that the theory has been very much strengthened by the recent important spectroscopic researches of ,mr4 ,lockyer and others in reference to the constitution of nebul4 ,the ,second ,part of the work deals with the evidence in support of the theory derived from the testimony of geology and biology as to the age of the sun's heat4 ,the ,third1 and last1 ,part has been devoted to questions relating to the pre-nebular condition of the universe1 and the bearing which these have on theories of stellar evolution4 ,several subjects introduced in this part are only very briefly treated4 ,these will1 however1 be considered at greater length in a future volume1 8,determinism1 not ,force1 the ,foundation-stone of ,evolution10 a work of a more general and abstract character1 which was commenced many years ago4 ,,perth3 ,january #b1 #ahhi4 ---------------------------------------- -------------------------------- ,,contents4 ,illustration ---------------------------------------- -------------------------------- ,,part ,i4 ,,the ,,impact ,,theory ,,of ,,stellar ,,evolution4 ,,page ,,consideration ,,of ,,the ,,facts ,,which ,,support ,,the ,,theory1 ,,and ,,of ,,the ,,light ,,which ,,the ,,theory ,,appears ,,to ,,cast ,,upon ,,the ,,facts #ab ,i4 ,probable ,origin of ,meteorites #ab ,,ii4 ,motion of the ,stars2 how of such different velocities1 and always in straight lines #ad ,,iii4 ,motion of the ,stars not due to their mutual attractions #ad ,,iv4 ,probable ,origin of ,comets #ag ,v4 ,nebul #ah #a4 ,origin of ,nebul #ah #b4 ,how ,nebul occupy so much space #ah #c4 ,why ,nebul are of such various shapes #ai #d4 ,broken fragments in a ,gaseous mass of an excessively high temperature the ,first stage of a ,nebula #ai #e4 ,the ,gaseous condition the ,second stage of a ,nebula #bd #f4 ,the ,gaseous condition ,essential to the ,nebular ,hypothesis #be #g4 ,the mass must have possessed an excessive temperature #bf #h4 ,gravitation could1 under no possible condition1 have generated the ,amount of ,heat required by the ,nebular ,hypothesis #bg #i4 ,condensation the ,third and last stage of a ,nebula #cj #aj4 ,how ,nebul emit such feeble ,light #cj ,,vi4 ,binary ,systems #cb ,,vii4 ,sudden ,outbursts of ,stars #cc ,,viii4 ,star ,clusters #cd ,,ix4 ,age of the ,sun's ,heat3 a ,crucial ,test #cd ,,part ,,ii4 ,,evidence ,,in ,,support ,,of ,,the ,,theory ,,from ,,the ,,age ,,of ,,the ,,sun',s ,,heat4 ,,testimony ,,of ,,geology ,,and ,,biology ,,as ,,to ,,the ,,age ,,of ,,the ,,sun',s ,,heat #cg ,testimony of ,geology3 ,method employed #ci ,the ,average ,rate of ,denudation in the ,past probably not much greater than at the ,present #dd ,how the ,method has been applied #dg ,method as applied by ,professor ,haughton #ej ,method as applied by ,mr4 ,alfred ,r4 ,wallace #ea ,method as applied directly #eb ,evidence from 8faults0 #ec ,time required to effect the foregoing amount of ,denudation #fb ,age of the ,earth as determined by the ,date of the ,glacial ,epoch #fd ,testimony of ,biology #fe ,,part ,,iii4 ,,evidence ,,in ,,support ,,of ,,the ,,theory ,,from ,,the ,,pre-,,nebular ,,condition ,,of ,,the ,,universe4 ,professor ,a4 ,winchell on the pre-nebular condition of matter #ga ,mr4 ,charles ,morris on the pre-nebular condition of matter #ge ,sir ,william ,r4 ,grove on the pre-nebular condition of matter #gh ,evolution of the ,chemical ,elements1 and its ,relations to ,stellar ,evolution #hj ,sir ,benjamin ,brodie on the pre-nebular condition of matter #hd ,dr4 ,t4 ,sterry ,hunt on the pre-nebular condition of matter #he ,professor ,oliver ,lodge on the pre-nebular condition of matter #hg ,mr4 ,william ,crookes on the pre-nebular condition of matter #ij ,professor ,f4 ,w4 ,clarke on the pre-nebular condition of matter #ih ,dr4 ,g4 ,johnstone ,stoney on the pre-nebular condition of matter #ii ,,the ,,impact ,,theory ,,in ,,relation ,,to ,,the ,,foregoing ,,theories ,,of ,,the ,,pre-,,nebular ,,condition ,,of ,,matter #ajb ,the ,theories do not account for the ,motion of the ,stars #aje ,the ,theories do not account for the ,amount of ,heat required #ajf ,evolution of ,matter #ajg ,objection considered #aji ,can we on ,scientific grounds trace back the ,evolution of the ,universe to an ,absolute ,first condition8 #aaj ---------------------------------------- -------------------------------- ,,stellar ,,evolution4 ,illustration ,,part ,i4 ,,the ,,impact ,,theory ,,of ,,stellar ,,evolution4 ,upwards of twenty years ago#a the theory--or1 ,i should rather say1 the hypothesis--was advanced#b that our sun was formed from a hot gaseous nebula produced by the colliding of two dark stellar masses2 and that1 as the stars are suns like our own1 they in all likelihood had a similar origin4 ,the probability of this theory has been very much strengthened by the facts1 both astronomical and physical1 which have accumulated since the theory was enunciated4 ,before proceeding to the consideration of these facts1 and the conclusions to which they lead1 it will be necessary to give a statement of the fundamental principles of the theory4 ,footnote #a3 ,philosophical ,magazine1 ,may #ahfh2 ,climate and ,time1 chap4 xxi42 ,quarterly ,journal of ,science1 ,july #ahgg2 ,phil4 ,mag41 ,july #ahgh2 ,climate and ,cosmology1 chaps4 xvii4 xviii4 and xix4 ,footnote #b3 ,i prefer to use the term 8theory10 with the above understood qualification1 viz4 a theory in its hypothetical stage4 ,in the theory here discussed the truth of the nebular hypothesis1 which begins by assuming the existence of a solar nebulous mass1 is taken for granted4 ,the present theory deals not so much with the nebulous mass itself as with the formation of the nebula1 and with those causes which led to its formation4 ,for convenience of reference1 and to prevent confusion1 ,i have called it the 8,impact ,theory10 by which name it may be distinguished1 on the one hand1 from the nebular theory1 and1 on the other hand1 from the meteoric theory1 and all other theories which regard gravitation as the primary source of the solar energy4 ,the theory starts with the assumption that the greater part of the energy possessed by the universe exists or is stored up in the form of the motion of stellar masses4 ,the amount of energy which may thus be stored up is startling to contemplate4 ,thus a mass equal to that of the sun1 moving with a velocity of #dgf miles per second1 would possess1 in virtue of that motion1 energy sufficient1 if converted into heat1 to maintain the present rate of the sun's radiation for #ej1jjj1jjj years4#c ,there is nothing extravagant in the assumption of such a velocity4 ,a comet1 for example1 having an orbit extending to the path of the planet ,neptune1 approaching so near the sun as to almost graze his surface in passing1 would have a velocity within #hf miles of what we have assumed4 ,twice this assumed velocity would give #bjj1jjj1jjj years' heat2 four times the velocity would give #hjj1jjj1jjj years' heat2 and so on4 ,footnote #c3 ,pouillet's estimate of the rate of solar radiation is here taken4 ,we are at perfect liberty to begin by assuming the existence of stellar masses in motion2 for we are not called upon to explain how the masses obtained their motion1 any more than we have to explain how they came to have their existence4 ,if the masses were created1 they may as likely have been created in motion as at rest2 and if they were eternal1 they may as likely have been eternally in motion as eternally at rest4 ,eternal motion is just as warrantable an assumption as eternal matter4 ,when we reflect that space is infinite--at least in thought--and that1 for aught we know to the contrary1 bodies may be found moving throughout its every region1 we see that the amount of energy may be perfectly illimitable4 ,but1 illimitable as the amount of the energy may be1 it could be of no direct service while it existed simply as the motion of stellar masses4 ,the motion1 to be available1 must be transformed into heat3 the motion of translation into molecular1 or some other form of motion4 ,this can be done in no other way than by arresting the motion of the masses4 ,but how is such motion to be arrested8 ,how are bodies as large as our earth1 moving at the rate of hundreds of miles per second1 to have their motion stopped8 ,according to the theory this is effected by collision3 by employing the motion of the one body to arrest that of the other4 ,take the case of the formation of our sun according to the theory4 ,suppose two bodies1 each one-half of the mass of the sun1 moving directly towards each other with a velocity of #dgf miles per second4 ,these bodies would1 in virtue of that velocity1 possess #dadi #ajch foot-pounds of energy1 which is equal to #ajj1jjj1jjj1jjj foot-pounds per pound of the mass2 and this1 converted into heat by the stoppage of their motions1 would suffice to maintain1 as was previously stated1 the present rate of the sun's radiation for a period of #ej1jjj1jjj years4 ,it must be borne in mind that1 while #dgf miles per second is the velocity at the moment of collision1 more than one-half of this would be derived from the mutual attraction of the two bodies in their approach to each other4 ,coming in collision with such a velocity1 the result would inevitably be that the two bodies would shatter each other to pieces4 ,but1 although their onward motions would thus be stopped1 it is absolutely impossible that the whole of the energy of their motions could be at once converted into heat2 and it is equally impossible that it could be annihilated4 ,physical considerations enable us to trace1 though in a rough and general way1 the results which would necessarily follow4 ,the broken fragments1 now forming one confused mass1 would rebound against one another1 breaking up into smaller fragments1 and flying off in all directions4 ,as these fragments receded from the centre of dispersion they would strike against each other1 and1 by their mutual impact1 become shivered into still smaller fragments1 which would in turn be broken up into fragments yet smaller1 and so on as they proceeded outwards4 ,this is1 however1 only one part of the process1 and a part which would certainly take place1 though no heat were generated by the collisions4 ,a far more effective means of dispersing the fragments and shattering them to pieces would be the expansive force of the enormous amount of incandescent gas almost instantaneously generated by the heat of collision4 ,the general breaking up of the two masses and the stoppage of their motions would be the work of only a few minutes1 or a few hours at most4 ,the heat evolved by the arrested motion would1 in the first instance1 be mainly concentrated on the surface layers of the broken blocks4 ,the layers would be at once transformed into the gaseous condition1 thus enveloping the blocks and filling the interspaces4 ,it is difficult to determine what the temperature and expansive force of this gas would at the moment be1 but evidently it would be excessive2 for1 were the whole of the heat of the arrested motion distributed over the mass1 it would1 as has been stated1 amount to #ajj1jjj1jjj1jjj foot-pounds per pound of the mass--an amount sufficient to raise #bfd1jjj tons of iron #a ,c4 ,thus1 if we assume the specific heat of the gas to be equal to that of air 7viz4 #bcgd71 it would have a temperature of about #cjj1jjj1jjj ,c4 or more than #adj1jjj times that of the voltaic arc4 ,i hardly think it will be deemed extravagant to assume that at the moment after impact the temperature of the evolved gas would be at least as great as here stated4 ,if we assume it to be so1 it is obvious that the broken mass would1 by the expansive force of the generated gas1 be dispersed in all directions1 breaking up into fragments smaller and smaller as they knocked against one another in their progress outwards from the centre of dispersion2 and these fragments would1 at the same time1 become gradually converted into the gaseous state1 and gradually come to occupy a space as large as that embraced in our solar system4 ,in the course of time the whole would assume the gaseous condition1 and we should then have a perfect nebula--intensely hot1 but not very luminous4 ,as its temperature diminished1 the nebulous mass would begin to condense1 and ultimately1 according to the well-known nebular hypothesis1 pass through all the different phases of rings1 planets1 and satellites into our solar system as it now exists4 ,i am glad to find that the theory1 in one of its main features1 has been adopted by ,sir ,william ,thomson1#d the highest authority we have on all points relating to the source of the sun's heat4 ,footnote #d3 ,lecture on 8,the ,probable ,origin1 the ,total ,amount1 and the ,possible ,duration of the ,sun's ,heat10 delivered at the ,royal ,institution on ,january #ba1 #ahhg1 and published in ,nature of #bgth of the same month4 ,the lecture was afterwards published with considerable additions and alterations in the ,proceedings of the ,institution vol4 xii4 ,it is from this that my quotations are taken4 8,we cannot10 says ,sir ,william1 8help asking the question1 ,what was the condition of the sun's matter before it came together and became hot8 7#a7 ,it may have been two cool1 solid masses1 which collided with the velocity due to their mutual gravitation2 or 7#b71 but with enormously less of probability1 it may have been two masses colliding with velocities considerably greater than the velocities due to their mutual gravitation40 ,he adopts the first of these suppositions4 8,to fix the idea10 he continues1 8think of two cool1 solid globes1 each of the same mean density as the earth1 and of half the sun's diameter1 given at rest1 or nearly at rest1 at a distance asunder equal to twice the earth's distance from the sun4 ,they will fall together and collide in exactly half a year4 ,the collision will last for about half an hour1 in the course of which they will be transformed into a violently agitated incandescent fluid mass flying outward from the line of the motion before the collision1 and swelling to a bulk several times greater than the sum of the original bulks of the two globes4 ,how far the fluid mass will fly out all around from the line of collision it is impossible to say4 ,the motion is too complicated to be fully investigated by any known mathematical method2 but with sufficient patience a mathematician might be able to calculate it with some fair approximation to the truth4 ,the distance reached by the extreme circular fringe of the fluid mass would probably be much less than the distance fallen by each globe before the collision1 because the translational motion of the molecules constituting the heat into which the whole energy of the original fall of the globes becomes transformed in the first collision is probably about three-fifths of the whole amount of that energy4 ,the time of flying out would probably be less than half a year1 when the fluid mass must begin to fall in again towards the axis4 ,in something less than a year after the first collision the fluid will again be in a state of maximum crowding round the centre1 and this time probably even more violently agitated than it was immediately after the first collision2 and it will again fly outward1 but this time axially towards the places whence the two globes fell4 ,it will again fall inwards1 and after a rapidly subsiding series of quicker and quicker oscillations it will subside1 probably in the course of two or three years1 into a globular star of about the same dimensions1 heat1 and brightness1 as our present sun1 but differing from him in this1 that it will have no rotation40#e ,footnote #e3 ,proceedings of the ,royal ,institution1 vol4 xii4 p4 #ae4 ,this is precisely what ,i have been contending for during the past twenty years1 with the simple exception that ,i assume1 according to his second supposition1 that the 8two masses collided with velocities considerably greater than the velocities due to mutual gravitation40 ,sir ,william admits1 of course1 my supposition to be quite a possible one1 but rejects it on the supposed ground of its improbability4 ,his reasons for this1 stated in his own words1 are as follows3 8,this last supposition implies that1 calling the two bodies ,a and ,b for brevity1 the motion of the centre of inertia of ,b relatively to ,a must1 when the distance between them was great1 have been directed with great exactness to pass through the centre of inertia of ,a2 such great exactness that the rotational momentum or moment of momentum after collision was no more than to let the sun have his present slow rotation when shrunk to his present dimensions4 ,this exceedingly exact aiming of the one body at the other1 so to speak1 is1 on the dry theory of probability1 exceedingly improbable4 ,on the other hand1 there is certainty that the two bodies ,a and ,b at rest in space if left to themselves1 undisturbed by other bodies and only influenced by their mutual gravitation1 shall collide with direct impact1 and therefore with no motion of their centre of inertia1 and no rotational momentum of the compound body after the collision4 ,thus we see that the dry probability of collision between two neighbours of a vast number of mutually attracting bodies widely scattered through space is much greater if the bodies be all given at rest than if they be given moving in any random directions and with any velocities considerable in comparison with the velocities which they would acquire in falling from rest into collision40 ,sir ,william here argues that the second supposition is far less probable than the first1 because1 according to it1 the motion of the one body relatively to the other must1 in order to strike1 be directed with great exactness4 ,the result1 in such a case1 is that collision will rarely occur2 whereas1 according to the first supposition1 the two bodies starting from a state of rest will1 by their mutual gravitation1 inevitably collide4 ,according to the second hypothesis they will generally miss2 according to the first they will always collide4 ,i have been led to a conclusion directly opposed to ,sir ,william's4 ,the fact1 that1 according to the second supposition1 collisions can but rarely occur is one reason1 amongst others1 why ,i think that supposition to be true2 and the fact that1 according to the first supposition1 collisions must frequently occur is also one reason1 amongst others1 why ,i think it very improbable that it can represent the true condition of things4 ,it by no means adds anything to the probability of the first supposition to assert that1 according to it1 such collisions will occur readily and frequently4 ,on the contrary1 it would show that the supposition was the less likely to be true4 ,if the collisions were insufficient in character1 the fewer of them that occurred1 the better2 for the result of such collisions would simply be a waste of the potential energies of the universe4 ,we should in this case have an innumerable host of imperfect suns without planets1 or with at most only one or two1 and these at no great distance from the luminary4 ,there would thus be evolved a universe without any grand planetary systems4 ,there is still another objection to the supposition4 ,the same gravitating force which makes the dark bodies liable to come into collision with each other must1 of course1 make them equally liable to come into collision with the luminous bodies1 and with our sun amongst the rest4 ,our sun would1 accordingly1 be at the mercy of any of those masses which might happen to come within the reach of its attractive influence4 ,it would pull the mass towards it1 and a collision would be inevitable1 unless it so happened that a transverse motion of the sun itself might enable it to escape destruction4 ,even in such a case it could not by any means manage to get rid of the entangling mass4 ,all this risk1 in so far as gravitation is concerned1 would have been completely averted if an original projected velocity of some thirty or forty miles per second had been conferred on the dark mass2 for1 in this case1 the attractive force of the sun would fail to arrest its motion1 and the mass would pass onward through space1 never to return4 ,this simple conception of an original motion removes entirely those objections which1 we have seen1 besets the supposition we have been considering4 ,with such a motion1 not only would the risk to our solar system be removed1 but the collisions between the dark bodies themselves would be a matter of rare occurrence2 and hence the energy of the universe would be conserved4 ,and when a collision did happen it would be on a grand scale1 and the result would be not an imperfect sun without planets1 but an incandescent nebula1 out of which1 by condensation1 a complete solar system would be evolved4 ,in fact1 within the whole range of cosmical physics1 ,i know of nothing more impressive in its sublime simplicity than this plan1 by which the stability and perfection of the universe is thus secured4 ,how vast the ends--how simple the means6 ,,consideration ,,of ,,the ,,facts ,,which ,,support ,,the ,,theory1 ,,and ,,of ,,the ,,light ,,which ,,the ,,theory ,,appears ,,to ,,cast ,,upon ,,the ,,facts4 ,i4 ,probable ,origin of ,meteorites4 ,recent researches establish beyond doubt that stars1 nebul1 comets and meteorites1 do not differ much from our earth in their chemical constitution4 ,meteorites1 it is true1 differ in their physical characteristics from ordinary rock such as is found on the earth's surface4 ,but it is possible1 if not probable1 that the earth's interior mass 8may10 as ,sir ,henry ,roscoe remarks1 8partake of the physical nature of these metallic meteorites1 and that if we could obtain a portion of matter from a great depth below the earth's surface we should find it exactly corresponding in structure as well as in chemical composition with a metallic meteorite1 and the existence of such interior masses of metallic iron may go far to explain the well-known magnetic condition of our planet40#f ,i think there can be little doubt that1 were our earth broken up into small fragments1 and these scattered into space1 it would probably be impossible to distinguish them from ordinary meteorites4 ,the two would be so like in character that one can hardly resist the conviction that meteorites are but the fragments of sidereal masses which have been shattered by collision4 ,that meteorites are broken fragments is the opinion expressed by ,sir ,william ,thomson1 who says 8that he cannot but agree with the common opinion which regards meteorites as fragments broken from larger masses1 and that we cannot be satisfied without trying to imagine what were the antecedents of those masses40 ,the theory we have been considering appears to afford an explanation of their antecedents4 ,according to it1 they are broken fragments of two dark stellar masses which were shattered to pieces by collision4 ,after what has been stated concerning the production of the gaseous nebul out of which our solar system was formed1 it must be regarded as highly improbable1 if not impossible1 that the whole of the fragments projected outwards with such velocity should be converted into the gaseous condition4 ,multitudes of the smaller fragments1 especially those towards the outer circumference of the nebulous mass1 meeting with little or no obstruction to their onward progress1 would pass outwards into space with a velocity which would carry them beyond the risk of falling back into the nebula4 ,they would then continue their progress in their separated forms as meteorites4 ,if this be their origin1 then meteorites are the offspring of sidereal masses1 and not their parents1 as ,mr4 ,lockyer concludes4 ,footnote #f3 ,manchester ,science ,lectures1 ,fifth ,series1 p4 #ca4 ,these meteorites must be of vast antiquity1 for if they are fragments of the dark bodies then they must be not only older than our solar system1 but older than the nebula from which that system was formed4 ,some of them1 however1 may have come from other systems4 ,they are fragments which may yet cast some light on the history of the dark bodies4 ,comets1 bodies which in many points seem allied to meteorites1 probably have1 as we shall shortly see1 a similar origin4 ,,ii4 ,motion of the ,stars2 how of such different velocities1 and always in straight lines4 ,it will be only when the two bodies1 coming from contrary directions1 collide with equal momentum that the entire motion will be stopped4 ,but in the case of stellar masses moving1 as it were1 at random in every direction this is a condition which will but rarely occur4 ,accordingly1 in most cases the resulting stars will have more or less motion4 ,in short1 the stars should1 according to the theory1 be moving in all directions and with all varieties of velocity4 ,further1 it follows that these motions ought to be in perfectly straight lines1 and not in definite orbits of any kind4 ,so far as observation has yet determined1 all these conditions seem to be fulfilled4 ,sometimes it will happen that the two bodies will strike each other obliquely4 ,in this case the resulting star1 both as to the direction and velocity of its motion1 will1 to a large extent1 be the resultant of the two concurrent forces4 ,,iii4 ,motion of the ,stars not due to their ,mutual ,attractions4 ,according to the theory the absolute motion of the stars is due1 not to the influence of gravity1 but to motions which originally belonged to the two component masses out of which the star arose2 motion regarding the origin of which science can no more inform us than it can regarding the origin of the masses themselves4 ,there is strong presumptive evidence that the motion of the stars is due to this cause4 ,we know that there are stars which have a far greater velocity than can result from gravitation1 such1 for example1 as the star #ahcj ,groombridge1 which has a velocity of #bjj miles per second4 ,suppose1 with ,professor ,newcomb1 that the number of stars belonging to the universe amounts to #ajj1jjj1jjj1 and that these have1 on the average1 five times the mass of the sun1 and are spread out in a layer across which light requires #cj1jjj years to pass4 ,then computation shows that1 unless the attractive power of the whole were sixty-four times greater than it really is1 it could not have conferred on ,groombridge the motion which it possesses1 or arrest it in its onward course4#g ,we are therefore forced1 as ,professor ,newcomb remarks1 to one of two alternatives1 viz43 8,either the bodies which compose our universe are vastly more massive and numerous than telescopic examination seems to indicate1 or #ahcj ,groombridge is a runaway star1 flying on a boundless course through infinite space1 with such momentum that the attraction of all the bodies of the universe can never stop it40 ,footnote #g3 ,newcomb's ,astronomy1 p4 #dhg1 ,english edition1 #ahgh4 ,as regards the theory we are discussing1 it is the same which alternative is taken1 for both are equally favourable4 ,if the former1 then1 according to the theory that stellar heat had its origin in collision1 it is presumptive evidence that space is occupied by dark bodies far more numerous and massive than the luminous ones which the telescope reveals4 ,if the latter1 viz4 that the star has a velocity which never could have been produced by attraction1 8then10 as says ,professor ,newcomb1 8it must have been flying forward through space from the beginning1 and1 having come from an infinite distance1 must now be passing through our system for the first and only time40 ,the probability is1 however1 that the star derived its motion from the source from which it derived its light and heat2 namely1 from the collision of the two masses out of which it arose4 ,if the star is ever to be arrested in its onward course1 it must be by collision2 but such an event would be its final end4 ,there are other stars1 such as #fa ,cygni1 ,indi1 ,lalande #babeh1 ,lalande #baahe1 ,cassiopei1 and ,arcturus1 possessed of motions which could not have been derived from gravity4 ,and there are probably many more of which1 owing to their enormous distances1 the proper motions have not been detected4 ,centauri1 the nearest star in the heavens1 by less than one-half1 is distant twenty-one millions of millions of miles2 and there are1 doubtless1 many visible stars a thousand times more remote4 ,a star at this distance1 though moving transversely to the observer at the enormous rate of #ajj miles per second1 would take upwards of thirty years to change its position so much as one second1 and consequently #a1hjj years to change its position one minute4 ,in fact1 we should have to watch the star for a generation or two before we could be certain whether it was moving or not4 ,,iv4 ,probable ,origin of ,comets4 ,great difficulty has been experienced in accounting for the origin of comets upon the nebular hypothesis4 ,they approach the sun from all directions1 and their motions1 in relation to the planets1 are as often retrograde as direct4 ,not only are their orbits excessively elliptical1 but they are also inclined to the ecliptic at all angles from #j to #ij4 ,it is evidently impossible to account satisfactorily for the origin of comets if we assume them all to have been evolved out of the solar nebula1 although this has been attempted by ,m4 ,faye and others4 ,comets are evidently1 as ,laplace and ,professor ,a4 ,winchell both conclude1 strangers to our system1 and have come from distant regions of space4 ,if they belonged to the solar system they could not1 says ,professor ,winchell1 have parabolic and hyperbolic paths4 8,only a small portion of the comets10 he remarks1 8are known to move in elliptic orbits40#h ,this assumption that they are foreigners will account for all the peculiarities of their motions2 but how are we to account for their coming into our system8 ,how did they manage to leave that system in which they had their origin8 ,if a comet have come from one of the fixed stars trillions of miles distant1 the motion by which it traversed the intervenient space could not1 possibly1 have been derived from gravity4 ,we are therefore obliged to assume that the motion was a projected motion4 ,comets1 in all probability1 have the same origin as meteorites4 ,the materials composing them1 like those of the meteorites1 were probably projected from nebul by the expulsive force of the heat of concussion which produced the nebul4 ,some of them1 especially those with elliptic orbits1 may have possibly been projected from the solar nebula4 ,footnote #h3 ,world ,life4 p4 #bg4 ,v4 ,nebul4 ,it is a curious circumstance that the theory here advanced seems to afford a rational explanation of almost every peculiarity of nebul1 as ,i have1 on former occasions1 endeavoured1 at some length1 to prove4#i ,footnote #i3 ,philosophical ,magazine1 ,july #ahgh2 ,climate and ,cosmology1 ,chap4 xix4 #a4 ,origin of nebul4--,we have already seen that the theory affords a rational account of the origin of nebul4 #b4 ,how nebul occupy so much space4--,it accounts for the enormous space occupied by nebul4 ,it may be objected that1 enormous as would be the original temperature of the solar system produced by the primeval collision1 it would nevertheless be insufficient to expand the mass1 against gravity1 to such an extent that it would occupy the entire space included within the orbit of ,neptune4 ,but it will be perceived1 from what has already been stated regarding the dispersion of the materials before they had sufficient time to assume the gaseous condition1 that this dispersion was the main cause of the gaseous nebula coming to occupy so much space4 ,and1 to go farther back1 it was the suddenness and almost instantaneity with which the mass would receive the entire store of energy1 before it had time to assume even the molten1 not to say the gaseous1 condition1 which led to tremendous explosions1 followed by a wide dispersion of materials4 #c4 ,why nebul are of such varied shapes4--,although the dispersion of the materials would be in all directions1 it would1 according to the law of probability1 very rarely take place uniformly in every direction4 ,there would generally be a greater amount of dispersion in some directions than in others1 and the materials would thus be carried along various lines and to diverse distances2 and1 although gravity would tend to bring the widely scattered materials ultimately together into one or more spherical masses1 yet1 owing to the exceedingly rarified condition of the gaseous mass1 the nebul would change form but slowly4 #d4 ,broken fragments in a gaseous mass of an excessively high temperature the first stage of a nebula4--,from what has already been shown1 it will be seen that after the colliding of the two dark bodies the first condition of the resulting nebula would be an enormous space occupied by broken fragments of all sizes dashing against each other with tremendous velocities1 like the molecules in a perfect gas4 ,all the interspaces between those fragments would be entirely filled with a gaseous mass1 which1 at its earliest stages at least1 as in the case of the solar nebula1 would have a temperature probably more than one hundred thousand times that of the voltaic arc4 ,whether such a mass would be visible is a point which can hardly be determined1 as we can have no experience on earth of a gas at such a temperature4 ,that there are some of the nebul which appear to consist of solid matter interspersed in a gaseous mass is shown by the researches of ,mr4 ,lockyer#aj and others4 ,in fact1 the theory is held by ,professor ,tait#aa that nebul consist of clouds of stones--or meteor-swarms1 as ,mr4 ,lockyer would term them--in an atmosphere of hydrogen1 each stone of which1 moving about and coming into collision with some other1 is thereby generating heat which renders the circumambient gas incandescent4 ,in reference to this theory of ,professor ,tait1 ,mr4 ,lockyer says that the phenomena of the spectroscope can be quite well explained 8on the assumption of a cloud of stones1 providing always that you could at the same time show reasonable cause why these clouds of stones were #8banging about' in an atmosphere of hydrogen40#ab ,the theory1 however1 does not appear to afford any rational explanation of this banging about of the stones to and fro in all directions2 for1 according to it1 the only force available is gravitation1 and this can produce merely a motion of the materials towards the centre of the mass4 ,under these conditions very little impinging of the stones against each other would take place4 ,but1 according to the theory here adopted1 we have an agency incalculably more effective than gravity1 one which accounts not merely for the impact of the stones1 but for their very existence as such1 inasmuch as it explains both what they are and whence they came4 ,footnote #aj3 ,proceedings of ,royal ,society1 vol4 xliii4 p4 #aag4 ,footnote #aa3 ,good ,words for #ahge1 p4 #hfa4 ,footnote #ab3 ,manchester ,science ,lectures4 ,mr4 ,lockyer has recently fully adopted ,professor ,tait's suggestion as to the nature and origin of nebul1 and has endeavoured to give it further development4 ,he considers the nebul to be composed of sparse meteorites1 the collisions of which give the nebul their temperature and luminosity4 ,he divides the nebul into three groups1 8according as the formative action seems working towards a centre2 round a centre in a plane1 or nearly so2 or in one direction only40 ,as a result we have globular1 spheroidal1 and cometic nebul4 ,globular nebul he accounts for in the following manner4 8,if we10 he says1 8for the sake of the greatest simplicity consider a swarm of meteorites at rest1 and then assume that others from without approach it from all directions1 their previous paths being deflected1 the question arises whether there will not be at some distance from the centre of the swarm a region in which collisions will be most valid4 ,if we can answer this question in the affirmative1 it will follow that some of the meteorites arrested here will begin to move in almost circular orbits round the common centre of gravity4 8,the major axes of these orbits may be assumed to be not very diverse1 and we may further assume that1 to begin with1 one set will preponderate over the rest4 ,their elliptic paths may throw the periastron passage to a considerable distance from the common centre of gravity2 and if we assume that the meteorites with this common mean distance are moving in all planes1 and that some are direct and some retrograde1 there will be a shell in which more collisions will take place than elsewhere4 ,now1 this collision surface will be practically the only thing visible1 and will present to us the exact and hitherto unexplained appearance of a planetary nebula--a body of the same intensity of luminosity at its edge and centre--thus putting on an almost phosphorescent appearance4 8,if the collision region has any great thickness1 the centre should appear dimmer than the portion nearer the edge4 8,such a collision surface1 as ,i use the term1 is presented to us during a meteoric display by the upper part of our atmosphere40#ac ,footnote #ac3 ,proc4 of ,royal ,society1 vol4 xliv4 p4 #e4 ,spheroidal nebul1 he considers1 are produced by the rotation of what was at first a globular rotating swarm of meteorites4 ,cometic nebul are explained1 he considers1 8on the supposition that we have either a very condensed swarm moving at a very high velocity through a sheet of meteorites at rest1 or the swarm at rest surrounded by a sheet1 all moving in the same direction40 ,in an able and interesting work1 which seems almost utterly unknown in ,england1#ad ,professor ,winchell has advanced views similar to those of ,tait and ,lockyer regarding the nature and origin of nebul4 ,but he1 in addition1 discusses the further question of the origin of those swarms4 ,i shall have occasion to refer to ,professor ,winchell's views more fully when we come to the consideration of the pre-nebular condition of the universe4 ,footnote #ad3 ,world ,life1 or ,comparative ,geology1 by ,alexander ,winchell1 ,,ll4,d41 ,professor of ,geology and ,palontology in the ,university of ,michigan4 ,chicago3 ,s4 ,c4 ,griggs ,co4 #ahhc4 ,amongst the first to advance the meteoric hypothesis of the origin and formation of the solar system was probably the late ,mr4 ,richard ,a4 ,proctor4 ,this was done in his work1 8,other ,worlds than ,ours10 published in #ahgj4 8,under the continual rain of meteoric matter10 he says1 8it may be said that the earth1 sun1 and planets are growing4 ,now1 the idea obviously suggests itself that the whole growth of the solar system1 from its primal condition to its present state1 may have been due to processes resembling those which we now see taking place within its bounds40 ,he further adds3 8,it seems to me that not only has this general view of the mode in which our system has reached its present state a greater support from what is now actually going on than the nebular hypothesis of ,laplace1 but that it serves to account in a far more satisfactory manner for the principal peculiarities of the solar system4 ,i might1 indeed1 go farther1 and say that where those peculiarities seem to oppose themselves to ,laplace's theory they give support to those ,i have put forward40#ae ,he then goes on to show the points wherein his theory seems to him to offer a better explanation of those peculiarities than that of ,laplace4 ,footnote #ae3 ,other ,worlds1 chap4 ix4 #e4 ,the gaseous condition the second stage of a nebula4--,the second stage obviously follows as a necessary consequence from the first2 for the fragments1 in the case under consideration1 possess energy in the form of motion1 which1 with the heat of their circumambient vapour1 is more than sufficient not only to convert the fragments into the gaseous state1 but to produce complete dissociation of the chemical elements4 ,the complete transformation of the first stage into the second must1 therefore1 be simply a matter of time4 ,according to the laws of probability it may1 however1 sometimes happen that the two original dark bodies will not collide with force sufficient to confer on the broken fragments the energy required to convert them all into the gaseous condition4 ,the result in this case would1 no doubt1 be that the untransformed fragments1 drawn together by their mutual attractions1 would collide and form an imperfect star or sun1 without a planet4 ,such a star might continue luminous for a few thousands or perhaps a few millions of years1 as the case might be1 when it would begin to fade1 and finally disappear4 ,we have here an imperfect nebula1 resulting in an imperfect star4 ,in short1 we should have in those stellar masses1 on a grand scale1 what we witness every day around us in organic nature1 viz4 imperfect formations4 ,such occasional imperfections give variety and add perfection to the whole4 ,how dreary and monotonous would nature be1 were every blade of grass1 every plant1 every animal1 and every face we met formed after the most perfect model6 #f4 ,the gaseous condition essential to the nebular hypothesis4--,it is found that the density of the interior planets of our solar system compared with that of the more remote is about as five to one4 ,the obvious conclusion is that there is a preponderance of the metallic elements in the interior planets and of metalloids in the exterior4 ,it thus becomes evident1 as ,mr4 ,lockyer has so clearly shown1#af that when our solar system existed in a nebulous condition the metallic or denser elements would occupy the interior portion of the nebula and the metalloids the exterior4 ,taking a section of this nebula from its centre to its circumference1 the elements would in the main be found arranged according to their densities3 the densest at the centre1 and the least dense at the circumference4 ,if we compare the planets with their satellites1 we find the same law holding true4 ,the satellites of ,jupiter1 for example1 have a density of about only one-fifth of that of the planet1 or about one twenty-fifth of that of our earth1 showing that when the planet was rotating as a nebulous mass the more dense elements were in the central parts and the less dense at the outer rim1 where the satellites were being formed4 ,again1 if we take the case of our globe1 we find1 as ,mr4 ,lockyer remarks1 the same distribution of materials1 proving that when the earth was in the nebulous state the metallic elements chiefly occupied the central regions1 and the metalloids those outer parts which now constitute the earth's crust4 ,footnote #af3 ,manchester ,science ,lectures4 ,all these facts show that the sifting and sorting of the chemical elements according to their densities must have taken place when our solar system was in the condition of a nebula4 ,but1 further1 it seems impossible that this could have taken place had the materials composing the nebula been in the solid form1 even supposing that they had taken the form of clouds of stones4 ,it is equally impossible that the nebula could have been in the fluid or liquid state during this process4 ,this is obvious1 for the nebula must then have occupied1 at least1 the entire space within the orbit of the most remote planet4 ,but our solar system in the liquid condition could not occupy one-millionth part of that space4 ,it is therefore evident that the nebula must have been in the state of a gas1 and a gas of extreme tenuity4 #g4 ,the mass must have possessed an excessive temperature4--,there is ample evidence1 ,mr4 ,lockyer thinks1 to show that the temperature of the solar nebula was as great as that of the sun at the present time4 ,but ,i think it is extremely probable that1 in some of its stages1 the nebula had a very much higher temperature than that now possessed by the sun4 ,there must1 during the sifting period1 have been complete chemical dissociation1 so as to keep the metals and the metalloids uncombined1 and thus allow the elements to arrange themselves according to their densities4 ,the nebula hypothesis1 remarks ,mr4 ,lockyer1 8is almost worthless unless we assume very high temperatures1 because1 unless you have heat enough to get perfect dissociation1 you will not have that sorting out which always seems to follow the same law40 #h4 ,gravitation could1 under no possible condition1 have generated the amount of heat required by the nebular hypothesis4--,the nebular hypothesis does not profess to account for the origin of nebul4 ,it starts with matter existing in space in the nebulous condition1 and explains how1 by condensation1 suns1 planets c4 are formed out of it4 ,in fact1 it begins at the middle of a process3 it begins with this fine1 attenuated material in the process of being drawn together and condensed under the influence of attraction1 and professes to explain how1 as the process goes on1 a solar system necessarily results4 ,to simplify our inquiry we shall confine our attention to the solar nebula1 and consider in the first place how far condensation may be regarded as a sufficient source of heat4 ,a4 ,condensation4--,the heat which our nebula could have derived from condensation up to the time that ,neptune was detached from the mass1 no matter how far the outer circumference of the mass may have originally extended beyond the orbit of that planet1 could not have amounted to over #a_/g1jjj1jjj of a thermal unit 7#ggb foot-pounds7 for each cubic foot4 ,it is perfectly obvious that this amount could not have produced the dissociation required2 and without the required dissociation ,neptune could never have been formed4 ,further1 it is physically impossible that the materials of which our solar system are composed could have existed in the gaseous state in a cool condition prior to condensation4 ,unless possessed of great heat1 even hydrogen could not exist in stellar space in the gaseous form2 and far less could carbon1 iron1 platinum1 c4 ,before ,neptune could have been formed the whole of the materials of the system must have possessed heat1 not only sufficient to reduce them to the gaseous state1 but sufficient to produce complete dissociation4 ,but by no conceivable means could gravitation have conferred this amount of heat by the time that the mass had condensed to just within the limits of the orbit of ,neptune4 ,b4 ,solid globes colliding under the influence of gravity alone4--,as we have already seen1 the view has been adopted by ,sir ,w4 ,thomson that the solar nebula may have resulted from the colliding of cold1 solid globes with the velocity due to their mutual gravitation alone4 ,he states his views as follows3 8,suppose1 now1 that #bi1jjj1jjj cold1 solid globes1 each of about the same mass as the moon1 and amounting in all to a total mass equal to the sun's1 are scattered as uniformly as possible on a spherical surface of radius equal to one hundred times the radius of the earth's orbit1 and that they are left absolutely at rest in that position4 ,they will all commence falling towards the centre of the sphere1 and will meet there in #bej years1 and every one of the #bi1jjj1jjj globes will then1 in the course of half an hour1 be melted1 and raised to a temperature of a few hundred thousand or a million degrees ,centigrade4 ,the fluid mass thus formed will1 by this prodigious heat1 be exploded outwards in vapour or gas all round4 ,its boundary will reach to a distance considerably less than one hundred times the radius of the earth's orbit on first flying out to its extreme limit4 ,a diminishing series of out-and-in oscillations will follow1 and the incandescent globe1 thus contracting and expanding alternately1 in the course1 it may be1 of #cjj or #djj years1 will settle to a radius of forty times the radius of the earth's orbit40#ag ,footnote #ag3 ,proceedings of ,royal ,institution1 vol4 xii4 p4 #af4 ,the reason which he assigns for the incandescent globe settling down at a radius forty times that of the earth's orbit is as follows3 8,the radius of a steady globular gaseous nebula of any homogeneous gas is #dj per cent4 of the radius of the spherical surface from which its ingredients must fall to their actual positions in the nebula to have the same kinetic energy as the nebula has40 ,if the solar nebula thus produced would be swelled out into a spherical incandescent mass with a radius #dj times the radius of the earth's orbit1 simply because the globes fell from a distance of #ajj times the radius of that orbit1 then for a similar reason the mass would have a radius of #djj times that of the earth's orbit had the globes fallen from a distance of #a1jjj times the radius1 and #djj1jjj times if the globes had fallen from a distance of #a1jjj1jjj times the radius1 and two-fifths of any conceivable distance from which they may have fallen4 ,supposing all this to be physically possible1 which it undoubtedly is not1 still the heat generated would not be sufficient2 for1 whatever the radius of the nebula might be1 its entire energy1 both kinetic and potential1 is simply what is obtained from gravitation1 and this1 as we have seen1 is insufficient4 #i4 ,condensation the third and last condition of a nebula4--,according to the gravitation theory1 condensation is the first stage of a nebula as well as the last2 for1 according to it1 gravity is the force which both collects together the scattered materials and gives them their heat4#ah ,before condensation begins there can1 according to the gravitation theory1 be no such thing as a nebula properly so called4 ,the materials exist1 of course1 but they do not exist in the form of a nebula4 ,according to the impact theory which ,i here advocate1 condensation cannot begin till after the nebula has begun to lose the heat with which it was originally endowed4 ,footnote #ah3 ,laplace held a more accurate view of the primitive condition of the solar nebula4 ,he considered that1 owing to intense heat1 the solar mass became expanded to the limits of the remotest planetary orbit of our system2 that1 in cooling1 it began slowly to condense2 and that1 as condensation went on1 planet after planet became detached from the mass4 ,laplace1 however1 offered no explanation of the manner in which the primitive nebula obtained its heat4 #aj4 ,how nebul emit such feeble light4--,the light of nebul is mainly derived from glowing hydrogen and nitrogen in a condition of extreme gaseous tenuity2 and it is well known that these gases are exceedingly bad radiators4 ,the oxyhydrogen flame1 although its temperature is surpassed only by that of the voltaic arc1 gives a light so feeble as to be scarcely visible in daylight4 ,the small luminosity of nebul is1 however1 mainly due to a different cause4 ,the enormous space occupied by those bodies is not so much due to the heat which they possess as to the fact that their materials were dispersed into space before they had time to pass into the gaseous condition2 so that1 by the time that this latter state was assumed1 the space occupied was far greater than was demanded either by the temperature or by the amount of heat which they originally received4 ,if we adopt the nebular hypothesis of the origin of our solar system1 we must assume that our sun's mass1 when in the condition of a nebula1 extended beyond the orbit of the planet ,neptune1 and consequently filled the entire space included within that orbit4 ,even supposing ,neptune's orbit to have been its outer limit1 which1 obviously1 was not the case1 it would nevertheless have occupied #bgd1jjj1jjj1jjj times the space it does at present4 ,we shall assume1 as before1 that #ej1jjj1jjj years' heat was generated by the concussion4 ,of course1 there might have been twice or even ten times that quantity2 but it is of no importance what amount is in the meantime adopted4 ,enormous as #ej1jjj1jjj years' heat is1 it yet gives1 as we shall presently see1 only #cb foot-pounds of energy for each cubic foot4 ,the amount of heat due to concussion being equal1 as before stated1 to #ajj1jjj1jjj1jjj foot-pounds for each pound of the mass1 and a cubic foot of the sun at his present density of #adc weighing #hi pounds1 each cubic foot must have possessed #h1ijj1jjj1jjj1jjj foot-pounds4 ,but when the mass was expanded sufficiently to occupy #bgd1jjj1jjj1jjj times its original space 7which it would do when it extended to the orbit of ,neptune71 the heat possessed by each cubic foot would then amount to only #cb foot-pounds4 ,in point of fact it would not even amount to so much1 for a quantity equal to upwards of #bj1jjj1jjj years' heat would necessarily be consumed in work against gravity in the expansion of the mass1 all of which would1 of course1 be given back in the form of heat as the mass contracted4 ,during the nebulous condition1 however1 this quantity would exist in an entirely different form1 so that only #ai out of the #cb foot-pounds per cubic foot generated by concussion would then exist as heat4 ,the density of the nebula would be only #a_/af1bdh1afj that of hydrogen at ordinary temperature and pressure4 ,the #ai foot-pounds of heat in each cubic foot would thus be sufficient to maintain an excessive temperature2 for there would be in each cubic foot only #a_/ddj1jjj of a grain of matter4 ,but1 although the temperature would be excessive1 the quantity both of light and heat in each cubic foot would of necessity be small4 ,the heat being only #a_/ga of a thermal unit1 the light emitted would certainly be exceedingly feeble1 resembling very much the electric light in a vacuum-tube4 ,,vi4 ,binary ,systems4 ,the theory affords a rational explanation of the origin of binary stars4 ,binary stars1 in so far as regards their motion1 follow also1 of course1 as a consequence1 from the gravitation theory4 ,if two bodies come into grazing collision1 8they will10 says ,sir ,william ,thomson1 8commence revolving round their common centre of inertia in long elliptic orbits4 ,tidal interaction between them will diminish the eccentricities of their orbits1 and1 if continued long enough1 will cause them to revolve in circular orbits round their centre of inertia40#ai ,this conclusion was pointed out many years ago by ,dr4 ,johnstone ,stoney4 ,footnote #ai3 ,proceedings of ,royal ,institution1 vol4 xii4 p4 #ae4 ,,vii4 ,sudden ,outbursts of ,stars4 ,the case of a star suddenly blazing forth and then fading away1 such as that observed by ,tycho ,brahe in #aegb1 may be accounted for by supposing that the star had been struck by one of the dark bodies--an event not at all impossible1 or even improbable4 ,in some cases of sudden outbursts1 such as that of ,nova ,cygni1 for example1 the phenomenon may result from the star encountering a swarm of meteorites4 ,the difficulty in the case of ,nova ,cygni is to account for the very sudden decline of its brilliancy4 ,this might1 however1 be explained by supposing that the outburst of luminosity was due to the destruction of the meteorites1 and not to any great increase of heat produced in the star itself4 ,a swarm of meteorites converted into incandescent vapour would not be long in losing its brilliancy4 ,mr4 ,lockyer thinks that the outburst was produced by the collision of two swarms of meteorites1 and not by the collision of the meteorites with a previously existing star4#bj ,footnote #bj3 ,proceedings of the ,royal ,society1 vol4 xliii4 p4 #adj4 ,amongst the millions of stars occupying stellar space catastrophes of this sort may1 according to the theory1 be expected sometimes to happen1 although1 like the collisions which originate stars themselves1 they must1 doubtless1 be events of but rare occurrence4 ,,viii4 ,star ,clusters4 ,a star cluster will result from an immensely widespread nebula breaking up into a host of separate nuclei1 each of which becomes a star4 ,the irregular manner in which the materials would1 in many cases1 be widely distributed through space after collision would prevent a nebula from condensing into a single mass4 ,subordinate centres of attraction would be established1 as was long ago shown by ,sir ,william ,herschel in his famous memoir on the formation of stars2#ba and around these the gaseous particles would arrange themselves and gradually condense into separate stars1 which would finally assume the condition of a cluster4 ,footnote #ba3 ,philosophical ,transactions for #ahaa4 ,,ix4 ,age of the ,sun's ,heat3 a ,crucial ,test4 ,when we come to the question of the age of the sun's heat1 and the length of time during which that orb has illuminated our globe1 it becomes a matter of the utmost importance which of the two theories is to be adopted4 ,on the age of the sun's heat rests the whole question of geological time4 ,a mistake here is fundamental4 ,if gravitation be the only source from which the sun derived its heat1 then life on the globe cannot possibly date farther back than #bj1jjj1jjj years2 for under no possible form could gravitation have afforded1 at the present rate of radiation1 sufficient heat for a longer period4 ,it will not do to state in a loose and general way1 as has been frequently done1 that the sun may have been supplying our globe with heat at its present rate for #bj1jjj1jjj or #ajj1jjj1jjj years1 for gravitation could have done no such thing2 a period of #bj1jjj1jjj1 not #ajj1jjj1jjj1 years is the lowest which is admissible on that theory4 ,not even that length of time would be actually available2 for this period is founded on ,pouillet's estimate of the rate of solar radiation1 which has been proved by ,langley to be too small1 the correct rate being #ag times greater4 8,thus10 as says ,sir ,w4 ,thomson1 8instead of ,helmholtz's #bj1jjj1jjj years1 we have only #ab1jjj1jjj40 ,but the #ab1jjj1jjj years would not in reality be available for plant and animal life2 for undoubtedly millions of years would elapse before our globe could become adapted for either flora or fauna4 ,if there is no other source of heat for our system than gravitation1 it is doubtful if we can calculate on much more than half that period for the age of life on the earth4 ,professor ,tait probably over-estimates the time when he affirms 8that #aj1jjj1jjj years is about the utmost that can be allowed1 from the physical point of view1 for all the changes that have taken place on the earth's surface since vegetable life of the lowest known form was capable of existing there40#bb ,and this is certainly about all that can ever be expected from gravitation2 mathematical computation has demonstrated that it can give no more4 ,the other theory1 founded on motion in space--a cause as real as gravitation--labours under no such limitation4 ,according to it1 so far at least as regards the store of energy which may have been possessed by the sun1 plant and animal life may date back1 not to #aj1jjj1jjj years1 but to a period indefinitely more remote4 ,in fact1 there is as yet no known limit to the amount of heat which this cause may have produced2 for this depended upon the velocities of the two bodies at the moment prior to collision1 and what these velocities were we have no means of knowing4 ,they might have been #ejj miles a second1 or #e1jjj miles a second1 for anything which can be shown to the contrary4 ,of course ,i by no means affirm that it is as much as #ajj1jjj1jjj years since life began on our earth2 but ,i certainly do affirm that1 in so far as a possible source of the sun's energy is concerned1 life may have begun at a period as remote4 ,footnote #bb3 ,recent ,advances in ,physical ,sciences1 p4 #age4 ,,part ,,ii4 ,,evidence ,,in ,,support ,,of ,,the ,,theory ,,from ,,the ,,age ,,of ,,the ,,sun',s ,,heat4 ,,testimony ,,of ,,geology ,,and ,,biology ,,as ,,to ,,the ,,age ,,of ,,the ,,sun',s ,,heat4 ,the question which we have now to consider is--to which of the two theories does geology lend its testimony8 ,will the length of time which1 according to the gravitation theory1 can possibly be allotted satisfy the requirements of geology8 ,in short1 are the facts of geology reconcilable with the theory8 ,if not1 the theory must be abandoned4 ,before the period when geologists felt that they were limited to time by physical considerations1 the most extravagant opinions prevailed in regard to the length of geological epochs4 ,so long as the physicist continued to state in a loose and general way that the sun might have been supplying our earth with heat at his present rate for the past #ajj1jjj1jjj years1 no very serious difficulty was felt2 but when geologists came to understand that ten or twenty millions of years were all that could be granted to them1 the condition of matters was entirely altered4 ,the belief that the mathematical physicist must be right in his views as to the age of the sun's heat1 and that there is no possibility of a longer period being admitted1 seems at present to be leading geologists towards the opposite extreme in regard to the length of geological time4 ,attempts have been recently made to compress the geological history of our globe into the narrow space allotted by the physicist4 ,the attempt is hopeless1 as well as injurious to geological science4 ,what misleads is not the belief that gravitation could not possibly afford a supply of heat sufficient for more than #bj1jjj1jjj years1 for this is true2 it is the belief that there was no other source of heat than gravity4 ,we shall now consider the evidence which geology seems to afford as to the age of the sun's heat4 ,geology is quite competent to render aid on this point1 for the sun's heat must be at least as old as life on this globe2 and the record of the rocks tells us when this life first appeared4 ,we require1 however1 to be able to measure the time which has elapsed since these records were left4 ,what we want is absolute time2 not relative time4 ,much has been done by geologists in regard to relative time2 but this can be of no service to us in our present inquiry4 ,unfortunately very little trustworthy work has been done in the way of determining the absolute length of geological periods4 ,happily1 however1 great exactness of measure is not required4 ,a rough approximation to the truth will suffice for our present purpose4 ,if it can be shown to be more than fifteen or twenty millions of years since life first appeared on the earth1 it will as effectually prove that gravitation alone could not have been the source from which the sun derived his heat as if it were shown that that period was a thousand times more remote4 ,all we have to do is simply to assign an inferior limit to the age of life on the earth2 and this can be effectually done by means of the methods1 imperfect though they be1 which we have at command4 ,as the question of geological time is of some importance in relation to our present inquiry1 ,i shall consider it at some length4 ,testimony of ,geology3 method employed4--,what has subsequently proved to be a pretty successful method of measuring geological time suggested itself to my mind during the summer of #ahfe4 ,it then occurred to me that we might obtain a tolerably accurate measure of absolute geological time from the present rate of subarial denudation1 which might be ascertained in the following way3 ,the rate of subarial denudation must be equal to the rate at which materials are carried off the land into the sea2 and this is measured by the rate at which sediment is carried down by our river systems4 ,consequently1 in order to determine the present rate of subarial denudation1 we have only to ascertain the quantity of sediment annually carried down by the river systems4 ,this gives us the time required to remove any given quantity1 say one foot1 off the face of the country4 ,if we assume the rate to be pretty much the same during past geological ages1 we have a means of telling the time that was occupied in removing any known thickness of strata4 ,but as we never can be perfectly certain that the rate is the same in both cases1 the results can1 of course1 be regarded as only approximately true4 ,taking the quantity of sediment discharged into the sea annually by the ,mississippi river1 as determined by ,messrs4 ,brown and ,dickson1#bc ,i found that it amounted to one foot off the face of the country in #a1chh years1 and that1 at this rate of denudation1 our continents1 even if they had an elevation of #a1jjj feet1 would not remain above sea-level over #a1ejj1jjj years4#bd ,this was an exaggerated estimate of the quantity of sediment1 for ,i shortly afterwards found that far more accurate determinations were made by ,messrs4 ,humphreys and ,abbot1#be who were employed by the ,united ,states ,government to report upon the physics and hydraulics of the ,mississippi4 ,messrs4 ,brown and ,dickson had estimated the quantity of sediment at #bh1ahh1jhc1hib cubic feet1 whereas ,messrs4 ,humphreys and ,abbot found it to be only #f1gbd1jjj1jjj cubic feet1 or less than one-fourth that amount4 ,this gives one foot in #f1jjj years as the rate of denudation4 ,footnote #bc3 ,proceedings of the ,american ,association for the ,advancement of ,science for #ahdh4 ,footnote #bd3 ,philosophical ,magazine1 ,february #ahfg4 ,i was not aware at this time that ,mr4 ,alfred ,tylor had previously applied the same method to determine an entirely different point1 viz43 how much the sea-level is being raised by the sediment deposited on the sea-bottom4 ,mr4 ,tylor's paper1 entitled 8,on ,changes of the ,sea-,level effected by existing ,physical ,causes during stated ,periods of ,time10 appeared in the ,phil4 ,mag4 for ,april #ahec4 ,mr4 ,tylor came to the conclusion that the sea-level was being raised1 from this cause1 about #c inches in #aj1jjj years4 ,footnote #be3 ,report upon the ,physics and ,hydraulics of the ,mississippi4 ,at this time ,dr4 ,archibald ,geikie took up the question and went into the consideration of the subject in a most thorough manner2 and it is mainly through the instrumentality of his writings on the matter#bf that the method under consideration has gained such wide-spread acceptance among geologists4 ,after an examination of nearly all that is known regarding the amount of sediment carried down by rivers1 he drew up the following table1 showing the number of years required by seven rivers to remove one foot of rock from the general surface of their basins4 ,danube #f1hdf years ,mississippi #f1jjj ,nith #d1gbc ,ganges #b1ceh ,rhone #a1ebh ,hoang-,ho #a1dfd ,po #gbi ----- ----- ,mean #c1cgh years ,this gives a mean of #c1cgh years to remove one foot1 or a little over one-half the time taken by the ,mississippi4 ,this mean appears to be generally taken as representing the average rate of subarial denudation of the whole earth1 but it has1 ,i fear1 been rather too hastily adopted4 ,to estimate correctly the quantity of sediment annually discharged by a large river is a most difficult and laborious undertaking4 ,a perusal of the voluminous report of ,messrs4 ,humphreys and ,abbot1 extending over #fij pages1 which ,dr4 ,geikie justly styles a model of patient and exhaustive research1 will clearly show this1 and at the same time prove how skilfully and accurately the task allotted to them was performed4 ,footnote #bf3 ,trans4 of ,geol4 ,soc4 of ,glasgow1 vol4 iii42 ,jukes ,geikie's ,manual of ,geology1 chap4 xxv42 ,text ,book of ,geology1 p4 #dda4 ,the risk of making very serious errors in computing the amount of sediment discharged1 unless proper precautions are taken1 is well illustrated in the case of the determinations made by ,messrs4 ,brown and ,dickson1 to which reference has already been made4 ,although their report shows that they took great pains in order to arrive at correct results--in fact1 they computed the total annual quantity of sediment discharged to within a cubic foot--after all1 instead of being correct to this minute quantity1 they gave a total more than fourfold what it ought to be4 ,a somewhat similar discrepancy exists in reference to the denudation of the basin of the ,ganges4 ,the time required to lower its surface by one foot is1 according to one estimate1 #b1ceh years2 according to another1 #a1gea2 and according to a third1 only #a1adf years4 ,the first figure is probably nearest the truth4 ,still1 these differences show both the difficulty of the problem and the necessity of caution in adopting any of these results as correct4 ,by far the most trustworthy determinations of the whole are those of the ,mississippi by ,messrs4 ,humphreys and ,abbot1 which may be relied upon as not far from the truth4 ,but1 supposing the estimates in the foregoing table to be perfectly correct1 can we assume that their mean may be safely taken as probably representing the average rate of denudation of the whole earth8 ,i would most unhesitatingly reply1 ,certainly not4 ,the ,rhone and ,po are full of glacier mud from the ,alps2 and the amount of sediment which they carry down may give us the rate of denudation of ,switzerland1 but certainly not that of the whole earth1 or even of ,europe4 ,the same may be said of the ,ganges1 which is charged with the mud which it brings down from the ,himalaya ,mountains4 ,the ,hoang-,ho1 or ,yellow ,river1 is an exceptionally muddy river2 in fact1 it derives its name from the vast quantity of yellow mud held by its waters in a state of solution4 ,it was probably the exceptionally muddy character of the ,po1 the ,rhone1 the ,ganges1 and the ,yellow ,river which attracted attention1 and led to observations being made of the sediment they contain4 ,rivers more unsuitable than these to give us the average denudation of the earth's surface could not well be selected4 ,among the seven rivers in the table1 leaving out of account the small ,scottish stream1 the ,nith1 with its basin of only #bjj square miles1 there are only two1 the ,mississippi and the ,danube1 that drain countries which may be regarded as in every way resembling the average condition of the earth's surface4 ,i would choose the ,mississippi as being superior to the ,danube1 for two reasons3 7#a7 because the rate of denudation of its basin has been more accurately determined2 and 7#b7 because the area of its basin not only exceeds that of the ,danube as five to one1 but better fulfils the necessary conditions1 as ,sir ,charles ,lyell has so clearly shown4 8,that river10 says ,sir ,charles1 8drains a country equal to more than half the continent of ,europe1 extends through twenty degrees of latitude1 and therefore through regions enjoying a great variety of climate1 and some of its tributaries descend from mountains of great height4 ,the ,mississippi is also more likely to afford us a fair test of ordinary denudation1 because1 unlike the ,st4 ,lawrence and its tributaries1 there are no great lakes in which the fluviatile sediment is thrown down and arrested on its way to the sea40#bg ,there is no other river in the globe which to my mind better fulfils the required conditions4 ,it is no doubt true that the rate of denudation of the basin of the ,mississippi is probably less than that of ,switzerland1 ,norway1 and the ,himalayas1 where glaciers abound1 and certainly less than that of ,greenland and the ,antarctic continent2 but1 on the other hand1 this rate is certainly much greater than that of the whole continent of ,africa1 ,australia1 and large tracts of ,asia1 where the rainfall is much smaller4 ,one foot in #f1jjj years may1 therefore1 ,i think1 be safely taken as the average rate of denudation of the whole surface of the globe4 ,footnote #bg3 ,student's ,elements of ,geology1 p4 #ia4 ,the average rate of denudation in the past probably not much greater than in the present4--,the belief has long prevailed that the rate of denudation was much greater in past ages than it is now2 but ,i am unable to perceive any good grounds for concluding that such was the case at any time since the beginning of the ,palozoic period4 ,various reasons have1 however1 been assigned for this supposed greater rate2 and to the consideration of these ,i shall now very briefly refer4 ,it has been thought that at some remote epoch of the earth's history1 when the moon was much nearer and the day much shorter than now1 the rate of denudation would1 owing to the erosive power of the enormous tides which would then prevail1 be much greater than at the present day4 ,this1 however1 is very doubtful4 ,there is nothing in the stratified rocks which affords any support to the idea of great tidal waves having swept over the land1 at least since the time when life began on our globe4 ,such a state of things would have destroyed all animal life4 8,the ,palozoic sediments10 as ,professor ,a4 ,winchell remarks1 8have been deposited1 for the chief part1 in quiet seas4 ,the deep beds of limestones and shales are spread out in sheets continent-wide1 which testify unmistakably to placid waters and slow deposition40#bh ,but high tides1 not sweeping over the land1 would not increase the rate of denudation to the extent supposed4 ,high tides silt up a river channel more readily than they deepen it4 ,a higher tide would probably produce a greater destruction of sea-coast3 it would tend to increase the rate of marine denudation1 but this would not materially affect the general rate of denudation4 ,for1 as the present rate of marine denudation is to that of subarial denudation only as #a to about #a1gjj1bi it would take a very large increase in the rate of marine denudation to affect sensibly the general result4 ,suppose the rate of marine denudation to have been1 for example1 ten times as great during the ,palozoic age as it is now 7which it certainly was not71 it would only have shortened the time required to effect a given amount of denudation of the whole earth by #i years in #a1gjj1 i4e4 by little more than one-half per cent4 ,footnote #bh3 ,world ,life1 p4 #bfe4 ,footnote #bi3 ,see ,climate and ,time1 p4 #ccg4 ,again1 it is assumed that the greater rate of terrestrial rotation in the early ages would produce certain influences which would in turn bring about a greater amount of denudation4 ,the rate of rotation has been slowly decreasing for ages1 and in ,palozoic times it must1 of course1 have been greater than at present4 ,a more rapid rotation would increase the velocity of the trade and anti-trade winds1 and would thus tend to augment the action of those meteorological agents chiefly effective in the work of subarial denudation4 ,here again the testimony of geology is negative4 ,we have no geological grounds to conclude that the winds of ,palozoic times were stronger than those at the present day4 ,the heat was no doubt greater1 and perhaps there was more rain2 but1 on the other hand1 there would be less frost1 snow1 ice1 and other denuding agents4 ,there is one cause which would1 perhaps1 be more effective than any of the foregoing3 viz4 the periodic occurrence of glacial epochs4 ,when a country is buried under ice1 the erosion of the surface is great4 ,but it must be borne in mind that the influence of rain1 rivers1 and other denuding agents now in operation would then1 in the glaciated regions1 be almost nil4 ,besides1 the greater part of the materials ground off the rocks would be left on the land2 and1 when the ice disappeared1 it would be found in the form of a thick mantle of boulder clay--a mantle which would protect the rocky surface of the country for thousands and tens of thousands of years from further denudation4 ,this is shown by the fine stri on the rocky surface1 made perhaps more than #ej1jjj years ago1 remaining under the boulder clay as perfect as the day on which they were engraved4 ,but1 more than all this1 a very considerable part of the #a foot presently being removed off the country in #f1jjj years consists of the loose materials belonging to the glacial epoch1 such as sands1 gravels1 and boulder clay1 which are being swept off the surface by rain and river action4 ,were it not for this1 the present rate of subarial denudation would not be so high as it actually is4 ,taking all things into consideration1 it is1 ,i think1 obvious that the average rate of denudation since the beginning of ,palozoic times was probably not much greater than at the present day4 ,how the method has been applied4--,having determined what appears to be the probable average rate of subarial denudation1 we may now proceed to consider the way in which this rate has been applied to measure past geological time4 ,there are two ways in which it may be applied for this purpose4 ,it may 7#a7 be applied directly3 knowing the thickness of strata which may have been removed by denudation1 we can easily tell1 from that rate1 the time it required to effect their removal4 ,if we have evidence1 for example1 that at some epoch #a1jjj feet of stratified rock were carried away1 then1 on the assumption that the rate of denudation was the same at that epoch as now1 we have #a1jjj #f1jjj #f1jjj1jjj years as the required time4 7#b7 ,it may be applied indirectly3 knowing the thickness of the strata1 we may estimate the time required for their formation4 ,this is the way in which it has usually been applied1 but1 as we shall see1 it is the less satisfactory way of the two4 ,dr4 ,a4 ,geikie gives the land area of the globe as #eb1jjj1jjj square miles1 and that of water as #add1gab1jjj square miles4#cj ,we may thus take the proportion of land to water roughly as #a to #c2 about one-quarter of the earth's surface being land1 and three-quarters water4 ,one foot1 therefore1 removed off the surface of the land would cover the whole globe with a layer #c inches thick1 or the entire sea-bottom with a layer #d inches thick4 ,footnote #cj3 ,physical ,geography1 p4 #ajc4 ,if we knew the total quantity of stratified rock on the globe1 we could easily tell the time that would be required for its formation4 ,most geologists would1 ,i believe1 be inclined to admit that1 if spread uniformly over the entire globe1 it would form a layer of at least #a1jjj feet in thickness4 ,in such a case the time required for its deposition would be as follows3 #a1jjj #f1jjj #d #bd1jjj1jjj years4 ,this would not1 however1 represent the age of the stratified rocks4 ,it would only represent the time required to deposit the rocks which we have assumed to be now in existence4 ,the greater mass of sedimentary rocks has been formed out of previously existing sedimentary rocks1 and these again out of sedimentary rocks still older4 ,the oldest known sedimentary rocks are the ,laurentian2 but these are believed by geologists to have been formed from still older sedimentary rocks4 ,it is therefore evident that the materials composing our stratified beds must have passed through many cycles of destruction and re-formation4 ,the materials of some of the recent formations1 for example1 may have passed through denudation and deposition a dozen of times over4#ca ,the time required to have deposited at a given rate the present existing mass of sedimentary rocks is probably but a small fraction of the time required to have deposited at the same rate the total mass that has actually been formed4 ,few geologists1 ,i think1 who will duly reflect on the subject1 will deem it too much to say that the present existing stratified rocks have on an average passed at least thrice through the cycle of destruction and re-formation4 ,if this be admitted1 then the #a1jjj feet of stratified rock represent1 not a period of #bd1jjj1jjj years1 but a period three times as great1 viz4 #gb1jjj1jjj years4 ,footnote #ca3 ,it is this destruction of the stratified rocks which makes it so difficult to detect the marks of former glacial epochs1 and which has led to such prevailing misconceptions regarding the evidence which we ought to expect of those epochs4 ,see paper read before the ,geological ,society1 8,on ,prevailing ,misconceptions regarding the ,evidence which we ought to expect of former ,glacial ,periods10 ,january #bc1 #ahhi4 ,it is impossible to tell from geological data the actual age of the stratified rocks2 but this is not required4 ,what we require is1 as already stated1 not their actual age1 but an inferior limit to that age4 ,method as applied by ,professor ,haughton4--,professor ,haughton estimates the mass of the stratified rocks down to the time of the ,miocene ,tertiary period as being #agg1bjj feet in thickness1 and covering an area equal to that of the sea4 ,the present rate of subarial denudation he considers to be equal to one foot removed off the surface of the land in #c1jij years4 ,if the proportion of land to water be taken as #eb to #ade1 it thus requires #h1faf years to deposit one foot of sediment over the bed of the ocean1 and consequently this is the rate at which strata are at present being formed4 ,this would give #h1faf #agg1bjj #a1ebf1gej1jjj years for the age of the stratified rocks4 ,but he assumes the rate of denudation to have been ten times greater in geological time than at present4 ,this consequently reduces the age of the rocks to #aeb1fge1jjj years4 ,by adding one-third for the time which has elapsed since the ,miocene ,tertiary period he gets #bjj1jjj1jjj years as a minimum length of geological time4#cb ,footnote #cb3 ,physical ,geography1 p4 #id4 ,the validity of this result rests upon what appear to me to be two very doubtful assumptions4 ,it is assumed in his calculations that the total amount of strata formed during past ages 7not the amount presently remaining7 was equal to a mass #agg1bjj feet in thickness1 covering the entire area of the ocean4 ,this is certainly doubtful4 ,it may have been as great1 for anything that can be proved to the contrary2 but we have no evidence that it was so4 ,certainly there is no evidence that the rate of subarial denudation during past ages was ever ten times as great as it is now4 ,but how is a length of #bjj1jjj1jjj years to be reconciled with the age of the sun's heat8 ,the stratified rocks may be as old as this1 but assuredly they are not if gravitation was the only source from which the sun derived his energy4 ,method as applied by ,mr4 ,alfred ,r4 ,wallace4--,mr4 ,wallace adopts ,professor ,haughton's estimate of #agg1bjj feet for the maximum thickness of the sedimentary rocks4 ,but1 instead of supposing1 like ,professor ,haughton1 the products of denudation to be uniformly spread over the entire sea-bottom1 he supposes them spread over a belt of merely #cj miles broad1 extending along the entire coast-line of the globe1 which he estimates at #ajj1jjj miles4 ,this gives an area of #c1jjj1jjj square miles on which the denuded matter of the whole land area of #eg1jjj1jjj square miles is deposited4 ,these two areas are to one another as #a to #ai1 and thus it follows that deposition goes on #ai times as fast as denudation4 ,the rate of denudation he takes as one foot removed off the surface of the land in #c1jjj years1 so that the rate of deposition would be about one foot in #aeh years1 and consequently the time required to deposit the #agg1bjj feet of rock would be #agg1bjj #aeh #bg1iig1fjj years4 ,this is a period double what the gravitation theory of the source of the sun's energy can afford4 ,and if the rate of denudation be taken at one foot in #f1jjj years1 which is1 as we have seen1 probably nearer the truth1 then this would make the age of the stratified rocks #ef1jjj1jjj years4 ,there seems to be a little ambiguity about ,mr4 ,wallace's result4 ,do the #agg1bjj feet represent the quantity of rock which presently exists1 or do they represent the total quantity which has been formed during all past ages8 ,if the former1 then the #bh1jjj1jjj years are but a fraction of the time which must have been required2 for1 as we have been shown1 the materials composing the stratified rocks have1 on an average1 been deposited at least three or four times over4 ,if1 on the other hand1 the thickness is meant to represent the total quantity of rock which has been formed during the whole of past geological time1 then the question arises1 by what means could this quantity possibly be ascertained8 ,in other words1 how was the relation between the present quantity and the total quantity ascertained8 ,but in either case the result is wholly irreconcilable with the gravitation theory of the source of the sun's heat4 ,method as applied directly4--,we have seen that it is impossible to determine the actual age of the earth from the stratified rocks1 even if we knew with perfect accuracy their present total amount4 ,we have also seen that from the rate of deposition we cannot fix with any degree of certainty a minimum value for the age of these rocks4 ,we can1 however1 by means of the first or direct application of the method1 assign with tolerable accuracy1 as was shown on a former occasion1#cc a minimum age to the earth4 ,we can be far more certain of the time which must have been required to remove by denudation1 say1 a thousand feet of rock than we can possibly be of the time required to have deposited a thousand feet of sediment4 ,the thousand feet of sediment may1 under certain conditions1 have been deposited in a hundred years1 while under other conditions they may have required a million of years4 ,in fact1 nothing can be more uncertain than the rate of deposition3 it depends upon such a multitude of circumstances4 ,at the mouth of a great river1 for example1 a foot of sediment may be deposited in a single day1 whereas in some places1 as in mid-ocean1 it may require a million of years to deposit the same amount4 ,but in reference to subarial denudation no such uncertainty exists4 ,footnote #cc3 ,quart4 ,journ4 of ,science1 ,july #ahgg2 ,climate and ,cosmology1 chap4 xvii4 ,the utter inadequacy of a period of #bj1jjj1jjj years for the age of our earth is demonstrable from the enormous thickness of rock which is known to have been removed off certain areas by denudation4 ,i shall now briefly refer to a few of the many facts which might be adduced on this point4 ,evidence from 8faults40--,one plain and obvious method of showing the great extent to which the general surface of the country has been lowered by denudation is furnished1 as is well known1 by the way in which the inequalities of surface produced by faults or dislocations have been effaced4 ,it is quite common to meet with faults where the strata on the one side have been depressed several hundreds--and in some cases thousands--of feet below those on the other2 but we seldom find any indications of such on the surface1 the inequalities on the surface having been all removed by denudation4 ,now1 in order to effect this1 a mass of rock must have been removed equal in thickness to the extent of the dislocation4 ,the following are a few examples of large faults3 ,the great ,irwell fault1 described by ,professor ,hull1#cd which stretches from the ,mersey west of ,stockport to the north of ,bolton1 has a throw of upwards of #c1jjj feet4 ,some remarkable faults have been found by ,professor ,ramsay in ,north ,wales4 ,for example1 near ,snowdon1 and about a mile ,e4,s4,e4 of ,beddgelert1 there is a fault with a downthrow of #e1jjj feet2 and in the ,berwyn ,hills1 between ,bryn-mawr and ,post-gwyn1 there is one of #e1jjj feet4 ,in the ,aran ,range there is a great fault1 designated the ,bala fault1 with a downthrow of #g1jjj feet4 ,again1 between ,aran ,mowddwy and ,careg ,aderyn the displacement of the strata amounts to no less than from #aj1jjj to #aa1jjj feet4#ce ,here we have evidence that a mass of rock1 varying from one to two miles in vertical thickness1 must have been denuded in many places from the surface of the country in ,north ,wales4 ,the fault which passes along the east side of the ,pentlands is estimated to have a throw of upwards of #c1jjj feet4#cf ,along the flank of the ,grampians a great fault runs from the ,north ,sea at ,stonehaven to the estuary of the ,clyde1 throwing the ,old ,red ,sandstone on end sometimes for a distance of two miles from the line of dislocation4 ,the amount of the displacement1 ,dr4 ,a4 ,geikie#cg concludes1 must in some places be not less than #e1jjj feet1 as indicated by the position of occasional outliers of conglomerate on the ,highland side of the fault4 ,the great fault crossing ,scotland from near ,dunbar to the ,ayrshire coast1 which separates the ,silurians of the ,south of ,scotland from the ,old ,red ,sandstone and ,carboniferous tracts of the ,north1 has been found by ,mr4 ,b4 ,n4 ,peach1 of the ,geological ,survey1#ch to have in some places a throw of fully #ae1jjj feet4 ,this great dislocation is older than the ,carboniferous period1 as is shown by the entire absence of any ,old ,red ,sandstone on the south side of the fault1 and by the occurrence of the ,carboniferous ,limestone and ,coal-measures lying directly on the ,silurian rocks4 ,we obtain here some idea of the enormous amount of denudation which must have taken place during a comparatively limited geological epoch4 ,so vast a thickness of ,old ,red ,sandstone could not1 as ,mr4 ,peach remarks1 8have ended originally where the fault now is1 but must have swept southwards over the ,lower ,silurian uplands4 ,yet these thousands of feet of sandstones1 conglomerates1 lavas1 and tuffs were so completely removed from the south side of the fault previous to the deposition of the ,carboniferous ,limestone series and the ,coal-measures1 that not a fragment of them is anywhere to be seen between these latter formations and the old ,silurian floor40#ci ,this enormous thickness of nearly three miles of ,old ,red ,sandstone must have been carried away during the period which intervened between the deposition of the lower members of the ,lower ,old ,red ,sandstone and the accumulation of the ,carboniferous ,limestone4 ,near ,tipperary1 in the south of ,ireland1 there is a dislocation of the strata of not less than #d1jjj feet1#dj which brings down the ,coal-measures against the ,silurian rocks4 ,here #a1jjj feet of ,old ,red ,sandstone1 #c1jjj feet of ,carboniferous ,limestone1 and #hjj feet of ,coal-measures have been removed by denudation off the ,silurian rocks4 ,not only has this immense thickness of beds been carried away1 but the ,silurian itself on which they rested has been eaten down in some places into deep valleys several hundreds of feet below the surface on which the ,old ,red ,sandstone rested4 ,footnote #cd3 ,mem4 ,geol4 ,survey of ,lancashire1 #ahfb4 ,footnote #ce3 ,mem4 ,geol4 ,survey of ,great ,britain1 vol4 iii4 ,footnote #cf3 ,memoir to ,sheet #cb1 ,geol4 ,survey ,map of ,scotland4 ,footnote #cg3 ,nature1 vol4 xiii4 p4 #cij4 ,footnote #ch3 ,explanation to ,sheet #ae1 ,geol4 ,survey ,map of ,scotland4 ,footnote #ci3 ,i have been informed by ,mr4 ,peach that since the above was written additional light has been cast on this immense fault4 ,it has been found1 he says1 that the fault consists of two sub-parallel branches1 the more southerly of which has the effect of bringing the rocks of the ,upper ,silurian age against the ,lower ,silurian beds4 ,the northern branch brings the upper division of the ,lower ,old ,red ,sandstones1 in turn1 against the ,upper ,silurian rocks4 ,this1 ,mr4 ,peach remarks1 does not in the least invalidate the reasoning as to the amount of material removed by denudation from this region in the time specified4 ,in fact1 it shows1 he says1 that a greater amount must have been removed than was at first suspected4 ,footnote #dj3 ,jukes's and ,geikie's ,manual of ,geology1 p4 #dda4 ,turning to the ,american continent1 we find the amount of rock removed to be even still greater4 ,in the ,valley of ,thessolon1 to the north of ,lake ,huron1 there is a dislocation of the strata to the extent of #i1jjj feet4#da ,in front of the ,chilowee ,mountains there is a vertical displacement of the strata of more than #aj1jjj feet4#db ,professor ,h4 ,d4 ,rogers found in the ,appalachian coal-fields faults ranging from #e1jjj feet to more than #aj1jjj feet of displacement4 ,in the ,nova ,scotia coal-fields one or two miles in thickness of strata have been removed in some places4#dc ,a great fracture runs along the axis of the ,sierra ,nevada for #cjj miles1 accompanied by a dislocation of #c1jjj to #aj1jjj feet4#dd ,the anticlinal of the ,park ,range of the ,rocky ,mountains was cleft down the axis1 and the eastern half depressed #aj1jjj feet4 ,and ,mr4 ,j4 ,p4 ,lesley gives an account of a fault in the ,appalachians of not less than #bj1jjj feet1 bringing the upper ,devonian strata on the one side opposite to the lowest ,cambrian on the other4#de ,a fault with a vertical displacement of #bj1jjj feet was found in the ,uinta ,mountains4#df ,in the ,aqui range of mountains1 ,utah1 there is a fault determined by ,mr4 ,s4 ,f4 ,emmons to be at least #aj1jjj feet4#dg ,the ,grand ,caon of ,colorado1 in some places #d1jjj1 #e1jjj1 and #f1jjj feet in depth1 is cut1 says ,professor ,a4 ,winchell1 in a plateau which has itself been lowered by erosion to the extent of #aj1jjj feet2 and this plateau occupies an area of #ac1jjj to #ae1jjj square miles4#dh ,the ,grand 8,wash ,fault10 ,colorado1 has a downthrow to the west of #f1jjj feet4 ,the 8,hurricane ,fault10 close to it1 has displaced the strata to the extent of over #ab1jjj feet4#di ,in the ,valley of ,east ,tennessee1 ,appalachian ,mountains1 it has been shown by ,mr4 ,j4 ,p4 ,lesley that as much as #ce1jjj feet of rock have been removed by denudation4 ,but this being from an anticlinal arch1 it does not1 of course1 afford any measure of the extent of the denudation of the surrounding country4 ,major ,j4 ,w4 ,powell1 ,director of the ,u4,s4 ,geol4 ,survey1 found that under a similar condition as much as three and a half miles of strata have been removed by denudation from the top of anticlinal beds in the ,uinta ,mountains4#ej ,probably the most enormous displacement of strata which has yet been found is that of the 8,wahsatch ,fault10 ,utah4 ,this fault is about #ajj miles in length1 crossing the fortieth parallel of latitude from north to south1 with a downthrow to the west of not less than #dj1jjj feet4 ,so clear is the evidence regarding this fault that ,mr4 ,clarence ,king says 8that there can be no doubt of the quantitative correctness of my reading of this tremendous dislocation40#ea ,there are other modes than the foregoing by means of which geologists are enabled to measure the thickness of strata which may have been removed in places off the present surface of the country4 ,into the details of these ,i need not here enter2 but ,i may give a few examples of the enormous extent to which the country1 in some places1 has been found to have been lowered by denudation4 ,dr4 ,a4 ,geikie has shown#eb that the ,pentlands must at one time have been covered with ,carboniferous rocks1 upwards of a mile in thickness1 which have all been removed by denudation4 ,in the ,bristol coal-fields1 between the river ,avon and the ,mendips1 ,sir ,andrew ,c4 ,ramsay has shown#ec that about #i1jjj feet of ,carboniferous strata have been removed by denudation from the present surface4 ,between ,bendrick ,rock and ,garth ,hill1 ,south ,glamorganshire1 a mass of ,carboniferous and ,old ,red ,sandstone1 of upwards of #i1jjj feet1 has been removed4 ,at the ,vale of ,towy1 ,caermarthenshire1 about #f1jjj feet of ,silurian and #e1jjj feet of ,old ,red ,sandstone--in all about #aa1jjj vertical feet--have been swept away4 ,between ,llandovery and ,aberaeron a mass of about #ab1jjj vertical feet of the ,silurian series has been removed by denudation4 ,between ,ebwy and the ,forest of ,dean1 a distance of upwards of #bj miles1 a thickness of rock varying from #e1jjj to #aj1jjj feet has been abstracted4 ,prof4 ,hull found#ed on the northern flanks of the ,pendle ,range1 ,lancashire1 the ,permian beds resting on the denuded edges of the ,millstone ,grit1 and these were again observed resting on the ,upper ,coal-measures south of the ,wigan coal-field4 ,now from the known thickness of the ,carboniferous series in this part of ,lancashire he was enabled to calculate approximately the quantity of ,carboniferous strata which must have been carried away between the period of the ,millstone ,grit and the deposition of the ,permian beds1 and found that it actually amounted to no less than #i1ijj feet4 ,he also found in the ,vale of ,clitheroe1 and at the base of the ,pendle ,range1 that the ,coal-measures1 the whole of the ,millstone ,grit1 the ,yoredale series1 and part of the ,carboniferous ,limestone1 amounting in all to nearly #bj1jjj feet1 had been swept away--an amount of denudation which1 as ,prof4 ,hull remarks1 cannot fail to impress us with some idea of the prodigious lapse of time necessary for its accomplishment4 ,footnote #da3 ,geology of ,canada1 #ahfc1 p4 #fa4 ,footnote #db3 ,safford's ,geology of ,tennessee1 p4 #cji4 ,footnote #dc3 ,lyell's ,student's ,manual1 chap4 xxiii4 ,footnote #dd3 ,geological ,studies1 by ,prof4 ,a4 ,winchell1 p4 #afe4 ,footnote #de3 ,geological ,studies1 pp4 #ic1 #afc4 ,footnote #df3 ,powell's ,geology of the ,uinta ,mountains4 ,footnote #dg3 ,geological ,exploration of the ,fortieth ,parallel1 vol4 ii4 p4 #def4 ,footnote #dh3 ,geological ,studies1 p4 #ib2 see also ,dutton's ,tertiary ,history of the ,caon ,district4 ,footnote #di3 ,tertiary ,history of the ,caon ,district1 pp4 #bj1 #aac2 ,second ,annual ,report1 ,u4,s4 ,geol4 ,survey1 p4 #abe4 ,footnote #ej3 ,powell's ,geology of ,uinta ,mountains4 ,footnote #ea3 ,geological ,exploration of the ,fortieth ,parallel1 vol4 i4 p4 #gde4 ,footnote #eb3 ,memoir to ,sheet #cb1 ,geol4 ,survey of ,scotland4 ,footnote #ec3 ,denudation of ,south ,wales4 ,memoirs of ,geol4 ,survey1 vol4 i4 ,footnote #ed3 ,quart4 ,journ4 ,geol4 ,soc4 vol4 xxiv4 p4 #cbc4 ,it may be observed that1 enormous as is the amount of denudation indicated by the foregoing figures1 these figures do not represent in most cases the actual thickness of rock removed from the surface4 ,we are necessitated to conclude that a mass of rock equal to the thickness stated must have been removed1 but we are in most cases left in uncertainty as to the total thickness which has actually been carried away4 ,it cannot be imagined that these great disruptions occurred first when the surface became subject to denuding agencies1 or that denudation ceased to operate precisely when the inequality was smoothed away4 ,moreover1 during the time the surface on one side of the fault was being reduced1 some amount of denudation must also have been in progress on the other and lower side4 ,in the case of a fault1 for example1 with a displacement of1 say1 one mile1 where no indication of it is seen at the surface of the ground1 we know that on one side of the fault a thickness of rock equal to one mile must have been denuded1 but we do not know how much more than that may have been removed4 ,for anything which we know to the contrary1 hundreds of feet of rock may have been removed before the dislocation took place1 and as many more hundreds after all indications of dislocation had been effaced at the surface4 ,but it must be observed that the total quantity of rock which has been removed from the present surface of the land is evidently small in proportion to the total quantity removed during the past history of our globe4 ,for those thousands and thousands of feet of rock which have been denuded were formed out of the waste of previously existing rocks1 just as these had been formed out of the waste of yet older rock-masses4 ,in short1 as a general rule1 the rocks of one epoch have been formed out of those of preceding periods1 and go themselves to form those of subsequent epochs4 ,in many of the cases of enormous denudation to which we have referred1 the erosion has been effected during a limited geological epoch4 ,we have1 for example1 seen that upwards of a mile in thickness of ,carboniferous rock has been denuded in the area of the ,pentlands4 ,but the ,pentlands themselves1 it can be proved1 existed as hills1 in much their present form1 before the ,carboniferous rocks were laid down over them2 and as they are of ,lower ,old ,red ,sandstone age1 and have been formed by denudation1 they must consequently have been carved out of the solid rock between the period of the ,old ,red ,sandstone and the beginning of the ,carboniferous age4 ,this affords us some conception of the immense lapse of time represented by the ,middle and ,upper ,old ,red ,sandstone periods4 ,again1 in the case of the great fault separating the ,silurians of the south of ,scotland from the ,old ,red ,sandstone tracts lying to the north1 a thickness of the latter strata of probably more than a mile1 as we have seen1 must have been removed from the ground to the south of the fault before the commencement of the ,carboniferous period4 ,and again1 in the case of the ,lancashire coal-fields1 to which reference has been made1 nearly two miles in thickness of strata had been removed in the interval which elapsed between the ,millstone ,grit and the ,permian periods4 ,time required to effect the foregoing amount of denudation4--,to lower the country one mile by denudation would therefore require1 according to the rate which we have already established1 about #ae1jjj1jjj years2 but we have seen that a thickness of rock more than equal to that must have been swept away since the ,carboniferous period2 and even during the ,carboniferous period itself more than a mile in thickness of strata in many places was removed4 ,again1 there can be no doubt whatever that the amount of rock removed during the ,old ,red ,sandstone period was much greater than one mile2 for we know perfectly well that over large tracts of country nearly a mile in thickness of rock was carried away between the period of the ,lower ,old ,red ,sandstone and the ,carboniferous epoch4 ,further1 all geological facts go to show that the time represented by the ,lower ,old ,red ,sandstone itself must have been enormous4 ,now1 three miles of rock removed since the commencement of the ,old ,red ,sandstone period 7which1 doubtless1 is an under-estimate7 would give us #de1jjj1jjj years4 ,again1 going farther back1 we find the lapse of time represented by the ,silurian period to be even more striking than that of the ,old ,red ,sandstone4 ,the unconformities in the ,silurian series indicate that many thousands of feet of these strata were denuded before overlying members of the same great formations were deposited4 ,and again1 this immense formation was formed in the ocean by the slow denudation of pre-existing ,cambrian continents1 just as these had been built up out of the ruins of the still prior ,laurentian land4 ,and even here we do not reach the end of the series1 for the ,laurentians themselves resulted from the denudation1 not of the primary rocks of the globe1 but of previously existing sedimentary and probably igneous rocks1 of which1 perhaps1 no recognisable portion now remains4 ,it is the opinion of ,mr4 ,darwin1 and also of ,mr4 ,wallace1 that the geological time which elapsed anterior to the ,cambrian period was as long as the whole interval from that period to the present day4 ,this is an opinion which ,i suppose is supported by most geologists4 ,but1 to err on the safe side1 ,i shall assume that the time which had elapsed prior to the ,old ,red ,sandstone was not greater than the time which has elapsed since that period4 ,even on this assumption we have at least #ij1jjj1jjj years as a minimum duration of geological time4 ,age of the earth as determined by the date of the glacial epoch4--,professor ,a4 ,winchell1 by a most careful examination of the probable relative lengths of geological periods1 arrived at the conclusion that the time which elapsed since the beginning of the glacial epoch is to the time which has elapsed since the solidification of the earth's surface as #a to #bej4ee ,according to the eccentricity theory of the cause of the glacial epoch1 that epoch began #bdj1jjj years ago2 consequently this makes the time since solidification took place #fj1jjj1jjj years1 a period which agrees roughly with that deduced from denudation1 and is so far presumptive evidence of the truth of that theory of the cause of the glacial cold4 ,footnote #ee3 ,world ,life1 p4 #cfi4 ,testimony of ,biology4--,the time required for the variation and modification of organic forms has1 ,mr4 ,alfred ,r4 ,wallace states1 been generally considered to require an even longer series of ages than might satisfy the demands of physical geology4 ,this is a point1 however1 on which ,i am not qualified to venture an opinion4 ,i shall simply refer to the views held by our highest authorities on the subject4 ,referring to ,professor ,huxley's anniversary address to the ,geological ,society in #ahgj1 where he shows that almost all the higher forms of life must have existed during the ,palozoic period1 ,mr4 ,wallace says3 8,thus1 from the fact that almost the whole of the ,tertiary period has been required to convert the ancestral ,orohippus into the true horse1 he1 ,professor ,huxley1 believes that1 in order to have time for the much greater change of the ancestral ungulata into the two great odd-toed and even-toed divisions 7of which change there is no trace even among the earliest ,eocene mammals71 we should require a large portion1 if not the whole1 of the ,mesozoic or ,secondary period4 ,another case is furnished by the bats and whales1 both of which strange modifications of the mammalian type occur perfectly developed in the ,eocene formation4 ,what countless ages back must we1 then1 go for the origin of these groups1 the whales from some ancestral carnivorous animal1 and the bats from the insectivora6 ,and even then we have to seek for the common origin of carnivora1 insectivora1 ungulata1 and marsupials at a far earlier period2 so that1 on the lowest estimate1 we must place the origin of the mammalia very far back in ,palozoic times40#ef 8,if the very small differences10 says ,professor ,huxley1#eg 8which are observable between the ,crocodilia of the older ,mesozoic formations and those of the present day furnish any sort of approximation towards an estimate of the average rate of change among the ,sauropsida1 it is almost appalling to reflect how far back in ,palozoic times we must go before we can hope to arrive at that common stock from which the ,crocodilia1 ,lacertilia1 ,ornithoscelida1 and ,plesiosauria1 which had attained so great a development in the ,triassic epoch1 must have been derived4 8,the ,amphibia and ,pisces tell the same story4 ,there is not a single class of vertebrated animals which1 when it first appears1 is represented by analogues of the lowest known members of the same class4 ,therefore1 if there is any truth in the doctrine of evolution1 every class must be vastly older than the first record of its appearance upon the surface of the globe4 ,but if considerations of this kind compel us to place the origin of vertebrated animals at a period sufficiently distant from the ,upper ,silurian1 in which the first ,elasmobranchs and ,ganoids occur1 to allow of the evolution of such fishes as these from a vertebrate as simple as the ,amphioxus1 ,i can only repeat that it is appalling to speculate upon the extent to which that origin must have preceded the epoch of the first recorded appearance of vertebrate life40 8,if the theory be true10 says ,mr4 ,darwin1 8it is indisputable that before the lowest ,cambrian stratum was deposited long periods elapsed--as long as1 or probably far longer than1 the whole interval from the ,cambrian age to the present day2 and that during these vast periods the world swarmed with living creatures40#eh ,in referring to the abundant and well-developed fauna of the ,cambrian period1 ,sir ,andrew ,c4 ,ramsay remarks3#ei 8,in this earliest known varied life we find no evidence of its having lived near the beginning of the ,zoological series4 ,in a broad sense1 compared with what must have gone before1 both biologically and physically1 all the phenomena connected with this old period seem1 to my mind1 to be quite of a recent description2 and the climates of seas and lands were of the very same kind as those that the world enjoys at the present day--one proof of which1 in my opinion1 is the existence of great glacial boulder beds in the ,lower ,silurian strata of ,wigtonshire1 west of ,loch ,ryan40 ,professor ,haeckel remarks that 8,darwin's theory1 as well as that of ,lyell1 renders the assumption of immense periods absolutely necessary4 ,if the theory of development be true at all1 there must certainly have elapsed immense periods1 utterly inconceivable to us40 ,in reference to the foregoing1 ,mr4 ,wallace says3#fj 8,these opinions1 and the facts on which they are founded1 are so weighty that we can hardly doubt that1 if the time since the ,cambrian epoch is correctly estimated at #bjj1jjj1jjj of years1#fa the date of the commencement of life on the earth cannot be much less than #ejj1jjj1jjj2 while it may not improbably have been longer1 because the reaction of the organism under changes of the environment is believed to have been less active in low and simple than in high and complex forms of life1 and thus the processes of organic development may for countless ages have been excessively slow40 ,footnote #ef3 ,island ,life1 p4 #bjd4 ,footnote #eg3 ,quart4 ,journ4 of ,geol4 ,soc4 vol4 xxvi4 p4 #ec4 ,footnote #eh3 ,origin of ,species1 p4 #bhf4 ,footnote #ei3 ,proceedings of the ,royal ,society1 ,no4 #aeb1 #ahgd1 p4 #cdb4 ,footnote #fj3 ,island ,life1 p4 #bje4 ,footnote #fa3 ,of course1 ,mr4 ,wallace does not believe that it is actually #bjj1jjj1jjj years since the ,cambrian period4 ,i think it must now be perfectly evident that the facts both of geology and of biology are utterly irreconcilable with the theory that the sun's heat was derived from the condensation of its mass by gravitation2 and that the mistake in regard to geological time has been committed by the physicist1 and not by the geologist4 ,the grounds upon which the geologists and the biologists found the conclusion that it is more than #bj or #cj millions of years since life began on the earth are far more certain and reliable than the grounds upon which the physicist concludes that the period must be less4 ,the only real ground that the physicist has is that according to the theory which he holds of the origin of the sun's heat a longer period is not possible4 ,this might be considered good evidence were no other theory possible2 but there is another theory1 which accords with all the facts1 and consequently has a strong presumption in its favour4 ,,part ,,iii4 ,,evidence ,,in ,,support ,,of ,,the ,,theory ,,from ,,the ,,pre-,,nebular ,,condition ,,of ,,the ,,universe4 ,the nebular hypothesis1 strictly speaking1 is one simply intended to account for the origin of our solar system4 8,it is10 as remarks ,professor ,a4 ,winchell1 8primarily a genetic explanation of the phenomena of the solar system2 and accessorily a co-ordination1 in a common conception1 of the principal phenomena in the stellar and nebular firmament1 as far as human vision has been able to penetrate40#fb ,the theory starts with the assumption that all the materials composing the solar system once existed in a state of extreme tenuity and diffusion1 filling far more than the entire space included within the orbit of the most remote planet4 ,it begins with this diffused nebulous mass tending slowly1 under the influence of gravitation1 towards a state of aggregation4 ,beyond this point the received nebular hypothesis does not extend4 ,footnote #fb3 ,world ,life1 p4 #aif4 ,it will be observed that the theory here begins in the middle of a process4 ,it begins with the assumption of a mass in the act of condensing under the influence of gravity4 ,it offers no explanation of the origin of the mass1 or how it came to be in this attenuated state1 or in what condition it existed before the materials began to draw together4 ,these are1 however1 inquiries which naturally force themselves on our attention4 ,if the nebular theory be a true theory of the origin of the solar system1 then this nebulous mass must have had an antecedent history1 and we cannot help feeling the instinctive desire of tracing the chain of causation farther back4 ,the mind presses towards an absolute beginning4 ,it is the goal to which it aspires1 and no amount of failure will ever deter it from renewing its efforts4 ,of recent years a considerable amount of attention has been devoted to inquiries in this direction2 nearly all of which1 it is true1 has necessarily been of a speculative and hypothetical character4 ,but hypothesis1 as ,mr4 ,locyker remarks1 is the life-blood of investigation4 ,the nebular hypothesis is so highly probable as to have gained almost universal acceptance4 ,in fact1 it contains very little of a hypothetical nature4 ,it is1 as ,mr4 ,mill says1 8an example of legitimate reasoning from a present effect to its past cause1 according to the known laws of that cause40 ,like the hypothesis of a luminiferous ether1 if it is not a true theory1 one would almost think that it deserves to be so4 ,there seems no reason why inquiries should stop at the point where ,laplace began4 ,the same line of reasoning may yet carry us back into the pre-nebular region1 and perhaps with as great a degree of certainty as it has done in the nebular2 though1 no doubt1 the farther back we proceed1 the more difficult probably will the inquiry become4 ,but1 be all this as it may1 there can be little doubt that the path of investigation is a legitimate one1 and also one which is worthy of being traced out4 ,i shall now briefly refer to some of the leading views which have been expressed in regard to the pre-nebular history of the universe1 and shall afterwards consider the additional light which the theory discussed in this volume seems to cast on the subject4 ,the commonly received opinion is that the nebul were formed from ordinary matter existing in a high state of division1 and widely diffused through space4 ,the 8cosmical dust10 as it is called1 was the universal 8world-stuff10 out of which all things were supposed to be formed4 ,it is held that in receding backwards in pre-nebular times1 the smaller1 more simple1 and elementary the materials were4 ,out of this primitive cosmical dust1 or world-stuff1 by aggregation1 the materials became successively larger and more complex4 ,the theory of the origin of nebul1 on this principle1 has been clearly stated by ,professor ,winchell1 and ,i here give a brief outline of his views on the subject4 ,professor ,a4 ,winchell on the pre-nebular condition of matter4--,this cosmical dust1 or world-stuff1 he considers to be scattered promiscuously through boundless space4 ,it is cold and non-luminous1 and is acted upon by forces of attraction and probably of repulsion4 ,the material particles1 either as atoms or less probably as molecules1 are drawn by mutual attraction into groups and swarms4 ,any central attractive force1 as of a sun or planet1 by causing the particles to move in converging lines1 would cause them to become approximated and ultimately aggregated4 ,thus both mutual attractions and centric movements would tend to produce aggregations dispersed through space4 ,but in the presence of two or more attractive centres1 as in the present constitution of the ,cosmos1 it is impossible that any mass shall fall directly upon its centre of attraction4 ,hence motions of rotation will be established in the mass1 and also orbital motions of masses about each other4 ,in addition to the mutual attraction of the molecules1 the convergence of their paths towards centres of attraction must also tend to the formation of masses and swarms of masses and particles4 8,we have then10 he says1 8to picture indefinite space as pervaded by swarms of masses and particles of dark matter4 ,each mass or particle may1 nevertheless1 be separated by thousands of miles4 ,it is manifest1 therefore1 that each mass or particle will eventually dispose itself1 under the fixed action of the forces of matter1 in some definite order4 ,it is manifest also1 from what has been said1 that each swarm will have a progressive motion along a path having the essential character of an orbit around some dominant centre of attraction4 ,if1 as seems to be the fact1 an ethereal medium1 or any condition of interplanetary matter1 exists in space1 it opposes the movements of these swarms by opposing the motion of each constituent mass4 ,but the smaller masses--the particles and molecules--would feel this resistance to the greatest extent4 ,they would therefore fall behind the heavier masses1 and would be most deflected toward the attracting centre4 ,the smallest particles would be driven farthest to the rear1 and dispersed farthest from the orbit of the train1 along the side turned toward the principal attraction4 ,the swarm would present an elongated form1 in which the larger and heavier masses would move foremost1 and nearest the line of the orbit--that is1 near the exterior skirt of the area covered by the general swarm--while the smaller ones would follow1 in graduated succession1 in a long train which would present a fan-like expansion lying mostly on the inside of the path of the principal masses40 8,this1 it may be conceived1 is the mode of aggregation of these cosmical matters in the depths of space4 ,of course the attractions which control them are feeble2 their movements are slow1 the resistances are relatively inconsiderable1 and the elongation of the swarm is correspondingly inconspicuous4 ,what ,i have described is a tendency which would be present4 ,sometimes the controlling attraction would be only another cosmical swarm4 ,the two swarms would revolve similarly about their common centre of gravity1 while prolonged resistances would cause their slow approximation and final coalescence at the common centre of gravity4 ,sometimes the controlling attraction would be exerted by a distant sun1 around which it would slowly move1 continually gathering up additions of matter from the wide fields of space40 8,in most cases all controlling attraction would be feebly felt4 ,these clouds of cosmical dust would float practically poised in the midst of space1 and would gradually grow by the continued accession of new matter4 ,some of them would become aggregates of large dimensions1 and their attraction would be distinctly felt by other aggregates4 ,there would be a tendency of such aggregates to approach each other4 ,they might possibly approach along a straight line2 but more probably some third aggregation1 or some distant sun1 would deflect them into orbits about their common centre of gravity1 in which1 by prolonged collisions of cosmical matter1 they are brought to ultimate coalescence with each other4 ,or some other attractive disturbance affords such a resultant of actions as may bring them more directly together4 ,when these larger aggregations of world-stuff come together1 the result is an aggregation approaching the dimensions of the ,herschellian nebul40#fc ,footnote #fc3 ,world ,life1 p4 #gb4 ,in regard to the origin of the heat of the nebul1 ,i am glad to find that ,professor ,winchell1 to a certain extent1 adopts the views which ,i have so long entertained on the subject4 8,the thought10 he says1 8must already have suggested itself to the reader that the process of conglomeration affords an explanation of the intense heat which vaporises its substance1 and causes it to yield a spectrum of bright lines4 ,as the sudden compression of a portion of atmospheric air yields heat sufficient to ignite tinder1 or fuse and volatilise a descending meteor-mass1 so the precipitation of one planet upon another would liberate sufficient heat to reduce them both to a state of fusion1 or even of vapour4 ,still more must the intensest heat be generated by the impact of two nebulous masses1 one or both of which together may embrace more matter than all our planets and the sun combined--as much even as the matter of our entire visible firmament of stars4 ,one experiences a distinct feeling of relief in the discovery of such a possible means of ignition of nebul40 ,mr4 ,charles ,morris on the pre-nebular condition of matter4--,others again suppose matter to be present everywhere throughout space4 ,this view has been ingeniously advocated by ,mr4 ,charles ,morris in an article on 8,the ,matter of ,space10 which appeared in ,nature1 ,february #h1 #ahhc4 ,the hypothesis of an ether specially distinct from matter he considers to be a gratuitous assumption1 and one of the last surviving relics of eighteenth century science1 and1 unless it can be proved that highly disintegrated matter is positively incapable of conveying light vibrations1 there is no warrant for assigning this duty to a distinct form of substance4 ,but that matter exists in outer space in the same conditions as in planetary atmospheres he thinks is improbable4 ,its duty as a conveyer of radiant vibrations seems to require a far greater tensity1 and its disintegration is probably extreme4 ,assuming matter throughout the universe--here as condensed spheres1 and there in outer space as highly rarified substance--the atmospheric envelopes of the spheres1 he considers1 will gradually shade off into the excessively rare matter of mid-space4 ,matter may exist in countless conditions as to simplicity and complexity1 c41 but the base particle he assumes to be the same under all conditions4 ,in the spheres there is matter ranging from the simplest elementary gases1 through the mineral compounds of the solid surface1 to the highly compounded organic molecules4 ,in outer space the variation is in the opposite direction2 the matter existing there in a highly disintegrated condition4 ,every particle he considers to possess a certain amount of motor energy in the form of heat4 ,as the total amount of this energy in the universe remains unchanged1 a particle can only lose energy by transferring it to others4 ,this heat energy acts1 of course1 in opposition to gravity3 it tends to repel the particles from each other1 while gravity1 on the other hand1 tends to draw them together4 ,the former acts as a centrifugal1 the latter as a centripetal energy4 ,if the heat momentum of the particles be insufficient to constitute a centrifugal energy equal to the centripetal energy of gravitation1 then the material contents of space will be drawn into the attracting spheres as atmospheric substance1 and outer space1 in this case1 will be left destitute of matter4 ,if1 on the contrary1 the centrifugal energy of the particles be sufficient to resist gravitation1 then the particles will remain free1 and space will continue to be occupied with matter4 ,as has been stated1 the sum of motor energy in the universe remaining unchanged1 the aggregation of atmospheric substance around any planet resulting from the loss of motor energy must cause an increase of motor energy in the particles outside4 ,the theory seems to dispense with the necessity for assuming a luminiferous ether1 for the functions attributed to the ether may1 it is thought1 be performed by the particles themselves2 a view which has been advocated by ,euler1 ,grove1 and others4 ,the origin of nebul1 according to the theory1 is accounted for as follows3 8,the nebular hypothesis10 says ,mr4 ,morris1 8holds that the matter now concentrated into suns and planets was once more widely disseminated1 so that the substance of each sphere occupied a very considerable extent of space4 ,it even declares that the matter of the solar system was a nebulous cloud1 extending far beyond the present limits of that system4 ,from this original condition the existing condition of the spheres has arisen through a continued concentration of matter4 ,but this concentration was constantly opposed by the heat energy of the particles1 or1 in other words1 by their centrifugal momentum4 ,this momentum could only be got rid of by a redistribution of motor energy4 ,if1 for illustration1 the average momentum of the particles of the nebul was just equivalent to their gravitative energy1 then a portion of this energy must radiate or be conducted outwards ere the internal particles could be held prisoners by gravitation4 ,the loss of momentum inwardly must be correlated with an increase of momentum outwardly4 8,this is a necessary consequence of the heat relations of matter4 ,as substance condenses1 its capacity for heat decreases and its temperature rises1 hence a difference of temperature must constantly have arisen between the denser and the rarer portions of the nebulous mass1 and equality of temperature could be restored only by heat radiation4 ,this radiation still continues1 and must continue until condensation ceases and the temperatures of the spheres and space become equalised2 but this is equivalent to declaring that as the particles of the spheres decrease in heat momentum those of interspheral space increase1 and if originally the centrifugal and centripetal energies of matter approached equality they must become unequal1 centripetal energy becoming in excess in spheral matter1 centrifugal energy in the matter of space4 ,thus1 as a portion of the widely distributed nebulous matter lost its heat1 and became permanently fixed in place by gravitative attraction1 another portion gained heat1 became still more independent of gravity1 and assumed a state of greater nebulous diffusion than originally4 ,the condensing spheres only denuded space of a portion of the matter which it formerly held1 and left the remainder more thinly distributed than before4 ,the spheres1 in their concentration1 have emitted1 and are emitting1 a vast energy of motion4 ,this motor energy yet exists in space as a motion of the particles of matter1 which1 therefore1 press upon each other1 or seek to extend their limits1 with increasing vigour1 so that the elasticity of interspheral matter is constantly increasing40 ,sir ,william ,r4 ,grove on the pre-nebular condition of matter4--,amongst the first to advocate the view that ordinary matter is everywhere present in space was ,sir ,william ,r4 ,grove4 ,in a lecture delivered at the ,london ,institution as far back as ,january #ahdb1 he stated that it appeared to him that heat and light1 according to the undulatory theory1 were the result of the vibrations of ordinary matter itself1 and not that of a distinct ethereal fluid4 ,twenty years afterwards1 referring to the views he then advanced1 he says3 8,although this theory has been considered defective by a philosopher of high repute1 ,i cannot see the force of the arguments by which it has been assailed2 and1 therefore1 for the present1 though with diffidence1 ,i still adhere to it40#fd ,footnote #fd3 ,correlation of ,physical ,forces1 p4 #afd 7fifth edition71 #ahfg4 ,he adduces a great many facts and forcible arguments in support of his position4 ,he says that 8there appears no reason why the atmosphere of the different planets should not be1 with reference to each other1 in a state of equilibrium4 ,ether1 or the highly attenuated matter existing in the interplanetary space1 being an expansion of some or all of these atmospheres1 or of the more volatile portions of them1 would thus furnish matter for the transmission of the modes of motion which we call light1 heat1 c40 ,it is assumed in the theory1 of course1 that matter must form a universal planum4 ,sir ,william ,grove favours the idea that the universe is illimitable in extent1 a view held by many eminent thinkers4 ,,evolution ,,of ,,the ,,chemical ,,elements1 ,,and ,,its ,,relations ,,to ,,stellar ,,evolution4 ,we come now to the consideration of a subject which has a most important bearing on the question of stellar evolution1 viz4 the genesis and dissociation of the chemical elements4 ,the evolution of one element from another is1 it is true1 as yet but a mere hypothesis1 but it is an hypothesis well supported by a host of facts and considerations1 and held by a large number of our leading chemists and physicists4 8,the demonstrated unity of force10 says ,professor ,f4 ,w4 ,clarke1#fe 8leads us by analogy to expect a similar unity of matter2 and the many strange and hitherto unexplained relations between the different elements tend to encourage our expectations40 ,the hypothesis throws much light on some obscure points in stellar evolution4 ,in regard to this1 ,professor ,clarke justly remarks that 8it is plain that the nebular hypothesis would be doubled in importance1 and our views of the universe greatly expanded1 if it could be shown that an evolution of complex from simple forms of matter accompanied the development of planets from the nebul4 ,evolution could look for no grander triumph40 ,in fact1 it is difficult to understand how our sun and the stars could have been evolved from nebul without assuming an evolution of the chemical elements4 ,the true nebul show the presence of only two elements1 nitrogen and hydrogen1 but our sun contains more than a dozen of distinct elements1 and the planets more than three times that number4 ,how1 then1 could all these have arisen out of nebul composed simply of nitrogen and hydrogen8 ,the matter is plain if we assume an evolution of the elements4 ,footnote #fe3 ,popular ,science ,monthly for ,january #ahgc4 ,the stars have been classed into four groups1 which1 as ,professor ,clarke has remarked1 indicate different stages in the process of evolution4 ,the first class1 containing white stars like ,sirius1 show the predominance of hydrogen and a scarcity of the metallic elements4 ,in the second class the metallic elements become more numerous and the hydrogen less distinct2 while in the third class hydrogen is difficult to detect4#ff ,this seems to show a gradual development of the chemical elements as the star cools and grows older4 ,i shall now give a brief account of the views expressed on the subject by some of our leading physicists and chemists4 ,footnote #ff3 ,see also on this point ,mr4 ,lockyer's 8,bakerian ,lecture10 ,proc4 ,roy4 ,soc4 ,no4 #bff1 p4 #ba4 ,it will be observed1 in reference to the theories we have just considered1 that the process of evolution is supposed to take place from the smaller to the larger aggregates of matter4 ,beginning with an extreme condition of tenuity1 by aggregation1 the materials become successively larger and more complex4 ,in passing backwards in the process we find the aggregates becoming less and less till they reach the 8cosmical dust10 or 8fire-mist10 out of which the primitive nebul were supposed to be formed4 ,receding still farther back1 we have the universal atmosphere from which the fire-mist is assumed to have been derived4 ,this universal atmosphere1 though in a state of extreme tenuity1 is1 as we shall see1 supposed by some to be in a more elemental form than anything revealed to us in the laboratory4 ,the suggestion of the dissociation of the chemical elements and its application to stellar physics was1 ,i think1 first advanced by ,sir ,benjamin ,brodie in #ahff1 and more fully in #ahfg4 ,in the latter year views similar were considered more fully by ,dr4 ,t4 ,sterry ,hunt4 ,the question of the dissociation of elements has been ably discussed by ,mr4 ,lockyer in his various writings4 ,it has been suggested by ,mr4 ,lockyer that the coincidence of rays emitted by different chemical elements when subjected to very high temperatures affords evidence of a common element in the composition of the metals producing the coincident rays4 ,mr4 ,lockyer states that many trains of thought suggested by solar and stellar physics point to the hypothesis that the elements themselves1 or at all events some of them1 are compound bodies4#fg ,this view was also put forward by ,professor ,graham1 who says 8that it is conceivable that the various kinds of matter now recognised in different elementary substances may possess one and the same element or atomic molecule existing in different conditions of mobility4 ,the essential unity of matter10 he adds1 8is an hypothesis in harmony with the equal action of gravity upon all bodies40 ,similar views have been advocated by ,m4 ,dumas1 who based the suggestion of the composite nature of the elementary atoms on certain relations of atomic weights4 ,the composite nature of the chemical elements has also been maintained by ,henri ,sainte-,claire ,deville1 and also by ,berthelot1 who held that the atoms of the elements are the same1 and distinguished only by their modes of motion4 ,professor ,schuster1 in a paper read before the ,british ,association in #ahhj1 supports the view of the dissociation of the chemical elements4 ,footnote #fg3 ,proc4 ,roy4 ,soc4 vol4 xxviii4 p4 #afj4 ,that all the purely physical sciences will one day be brought under a few general laws and principles1 and the whole of the recognised chemical elements will be resolved into one or two material elements1 is a conclusion towards which physical science seems at present slowly tending4 ,there is certainly something fascinating in this view of the unity of nature4 ,there is in this idea more than a purely physical interest attached to it4 ,it has1 as ,i hope to show in a future work1 an important bearing on questions relating to the foundations of the true theory of evolution4 ,the question of the unity of the chemical elements is one1 however1 yet in a hypothetical condition4 ,professors ,liveing and ,dewar1 who have given attention to this subject1 say3 8,the supposition that the different elements may be resolved into simpler constituents1 or into a single one1 has long been a favourite speculation with chemists2 but1 however probable this hypothesis may appear priori1 it must be acknowledged that the facts derived from the most powerful method of analytical investigation yet devised give it scant support40#fh ,footnote #fh3 ,proc4 ,roy4 ,soc4 vol4 xxxii4 p4 #bcj4 ,sir ,benjamin ,brodie on the pre-nebular condition of matter4--,there are1 considers ,sir ,benjamin ,brodie1 very forcible reasons which lead us to suspect that chemical substances are really composed of a primitive system of elemental bodies1 analogous in their general nature to our present elements3 that some of those bodies which we speak of as elements may be compounds4 ,these ideal elements assumed by him1 he says1 8though now revealed to us by the numerical properties of chemical equations only as implicit and dependent existences1 we cannot but surmise may sometimes become1 or may in the past have been1 isolated and independent existences0--as1 for instance1 in the case of the sun1 where the temperature is excessive4 8,we may10 he further adds1 8consider that in remote ages the temperature of matter was much higher than it is now1 and that these other things ideal elements existed then in the state of perfect gases--separate existences--uncombined40#fi ,he then refers to certain observations of ,mr4 ,huggins and ,dr4 ,miller on the spectra of nebul where one of the lines of nitrogen was found alone2 and that this suggested to them that the line might have been produced by one of the elements of nitrogen2 and that nitrogen may therefore be compound4 ,he mentions as a significant fact that a large proportion of the class of elements which he has termed 8composite elements0 has not been found in the sun1 they having probably been decomposed by the intense heat4 ,footnote #fi3 ,ideal ,chemistry1 p4 #ef4 ,dr4 ,t4 ,sterry ,hunt on the pre-nebular condition of matter4--,a year after the foregoing views regarding chemical dissociation had been advanced by ,sir ,benjamin ,brodie1 ,dr4 ,t4 ,sterry ,hunt1 in a lecture on 8,the ,chemistry of the ,primeval ,earth10 delivered at the ,royal ,institution 7,may #ca1 #ahfg71 put forward1 apparently quite independently1 opinions on dissociation similar to those of ,brodie4 ,in this lecture he says3 8,i considered the chemistry of nebul1 sun1 and stars in the combined light of spectroscopic analysis and ,deville's researches on dissociation1 and concluded with the generalisation that the breaking-up of compounds1 or dissociation of elements1 by intense heat is a principle of universal application1 so that we may suppose that all the elements which make up the sun1 or our planet1 would1 when so intensely heated as to be in the gaseous condition which all matter is capable of assuming1 remain uncombined1 that is to say1 would exist together in the state of chemical elements1 whose further dissociation in stellar or nebulous masses may even give us evidence of matter still more elemental than that revealed in the experiments of the laboratory1 where we can only conjecture the compound nature of many of the so-called elementary substances40#gj ,and in his address at the grave of ,priestley he referred to the suggestion of ,lavoisier that hydrogen1 nitrogen1 and oxygen1 with heat and light1 might be regarded as simpler forms of matter from which all others are derived4 ,this suggestion was considered in connection with the fact that the nebul1 which we conceive to be condensing into suns and planets1 have hitherto shown evidences only of the presence of the first two of these elements1 which1 as is well known1 make up a large part of the gaseous envelope of our planet1 in the forms of air and aqueous vapour4 ,with this he connected the hypothesis advanced by ,grove1 8that our atmosphere and ocean are but portions of the universal medium which1 in an attenuated form1 fills the interstellary spaces2#ga and further suggested as a legitimate and plausible speculation that these same nebul and their resulting worlds may be evolved by a process of chemical condensation from this universal atmosphere1 to which they would sustain a relation somewhat analogous to that of clouds and rain to the aqueous vapour around us40 ,footnote #gj3 ,american ,journal of ,science1 vol4 xxiii4 p4 #abd4 ,footnote #ga3 8,our atmosphere10 says ,dr4 ,hunt1 8is not terrestrial1 but cosmical1 being a universal medium diffused throughout all space1 but condensed around the various centres of attraction in amount proportional to their mass and temperature1 the waters of the ocean themselves belonging to this universal atmosphere40 7,nature1 ,august #bi1 #ahgh1 p4 #dge47 ,similar views have been advocated by ,mr4 ,mattieu ,williams1 who says 8that the gaseous ocean1 in which we are immersed1 is but a portion of the infinite atmosphere that fills the whole solidity of space2 that links together all the elements of the universe1 and diffuses among them their heat and light1 and all the other physical and vital forces which heat and light are capable of generating40 7,fuel of the ,sun1 p4 #e47 ,in #ahed ,sir ,william ,thomson suggested the idea that the luminiferous ether was probably a continuation of our atmosphere1 though ,i do not think he continues to hold that opinion4 ,the first to advance this idea was1 undoubtedly1 ,newton1 who assumed interplanetary space to be universally filled with an ethereal medium 8much of the same constitution as air1 but far rarer1 subtler1 and more elastic40 ,professor ,oliver ,lodge on the pre-nebular condition of matter4--,some have gone still farther back and supposed that the material universe may have arisen out of the luminiferous ether--the hypothetical medium which is assumed to pervade all space4 ,the universal world-stuff scattered through boundless space may in an extreme state of attenuation be1 says ,professor ,winchell1 the ethereal medium1 and out of this semi-spiritual substance may have germinated the molecules of common matter4 8,it is certainly possible10 he says1 8to conceive these cosmical atoms as a rising-out of some transformation of the ethereal medium2 but we know too little of the nature of ether to ground a scientific inference of this kind40#gb ,footnote #gb3 ,world ,life1 p4 #ecc4 ,the ethereal origin of matter has been advocated by ,m4 ,saigey1 ,dr4 ,macvicar1 and others4 ,in a lecture by ,professor ,oliver ,lodge1 delivered at the ,london ,institution in ,december #ahhb1 he also advocates the ethereal origin of matter4 8,as far as we know10 to state his views in his own words1 8this ether appears to be a perfectly homogeneous1 incompressible1 continuous body1 incapable of being resolved into simple elements or atoms2 it is1 in fact1 continuous1 not molecular4 ,there is no other body of which we can say this1 and hence the properties of ether must be somewhat different from those of ordinary matter40 444 8,one naturally asks1 is there any such clear distinction to be drawn between ether and matter as we have hitherto tacitly assumed8 ,may they not be different modifications1 or even manifestations1 of the same thing80 ,he then adopts ,sir ,william ,thomson's theory of vortex atoms1 into the details of which ,i need not here enter4 ,in conclusion1 says ,professor ,lodge1 8,i have now endeavoured to introduce you to the simplest conception of the material universe which has yet occurred to man--the conception that it is of one universal substance1 perfectly homogeneous and continuous1 and simple in structure1 extending to the farthest limits of space of which we have any knowledge1 existing equally everywhere3 some portions either at rest or in simple irrotational motion1 transmitting the undulations which we call light2 other portions in rotational motion--in vortices1 that is--and differentiated permanently from the rest of the medium by reason of this motion4 8,these whirling portions constitute what we call matter2 their motion gives them rigidity1 and of them our bodies and all other material bodies with which we are acquainted are built up4 8,one continuous substance filling all space1 which can vibrate as light2 which can be sheared into positive and negative electricity2 which in whirls constitutes matter2 and which transmits by continuity1 and not by impact1 every action and reaction of which matter is capable4 ,this is the modern view of ether and its functions40#gc ,footnote #gc3 ,nature1 ,february #a1 #ahhc1 p4 #ccj4 ,there is this objection to ,professor ,lodge's theory3 it is purely hypothetical4 ,the vortex atoms are not only hypothetical1 but the substance out of which these atoms are assumed to be formed is also itself hypothetical4 ,we have no certain evidence that such a medium as is thus supposed exists1 or that a medium possessing the qualities attributed to it could exist4 ,in fact1 we have here one hypothesis built upon another4 ,the vortex theory appears to me to be beset by a difficulty of another kind1 viz4 that of reconciling it with the ,first ,law of ,motion4 ,according to that law no body possessing inertia can deviate from the straight line unless forced to do so4 ,a planet will not move round the sun unless it be constantly acted upon by a force deflecting it from the straight path4 ,a grindstone will not rotate on its axis unless its particles are held together by a force preventing them from flying off at a tangent to the curve in which they are moving4 ,centrifugal force must always be balanced by centripetal force4 ,the difficulty is to understand what force counterbalances the centrifugal force of the rotating material of the vortex-atom4 ,it is not because the centrifugal tendency of the rotating material is controlled by the exterior incompressible fluid1 for it offers no resistance whatever to the passage of the atom through it--in short1 in so far as the motion of the atom is concerned1 this fluid is a perfect void4 ,now1 if this fluid can offer no resistance to the passage of the atom as a whole1 how then does it manage to offer such enormous resistance to the materials composing the atom1 so as to continually deflect them from the straight path and compel them to move in a curve8 ,the centrifugal force of these vortex-atoms must be enormous1 for on it is assumed to depend the hardness or resistance of matter to pressure4 ,now the centripetal force which balances this centrifugal force must be equally enormous4 ,if1 then1 this perfect fluid outside the vortex-atom can exert this enormous force on the revolving material without being itself possessed of vortex-motion1 there does not seem to be any necessity for vortex-motion in order to produce resistance4 ,in short1 how is the existence of the atom possible under the physical conditions assumed in the theory8 ,how this may be1 like the space of four dimensions1 may be expressed in mathematical language1 but like it1 ,i fear1 it is unthinkable as a physical conception4 ,mr4 ,william ,crookes on the pre-nebular condition of matter4--,in his opening address before the ,chemical ,section of the ,british ,association in #ahhf1 ,mr4 ,william ,crookes entered at considerable length into the question of the genesis and evolution of the chemical elements4 ,i shall here give a brief statement of his views as embodied in his important address1 and this ,i shall endeavour to do as nearly as possible in ,mr4 ,crookes's own words4 8,we ask10 says ,mr4 ,crookes1 8whether the chemical elements may not have been evolved from a few antecedent forms of matter--or possibly from only one such--just as it is now held that all the innumerable variations of plants and animals have been developed from fewer and earlier forms of organic life3 built up1 as ,dr4 ,gladstone remarks1 from one another according to some general plan4 ,this building up1 or evolution1 is above all things not fortuitous3 the variation and development which we recognise in the universe run along certain fixed lines which have been preconceived and foreordained4 ,to the careless and hasty eye design and evolution seem antagonistic2 the more careful inquirer sees that evolution1 steadily proceeding along an ascending scale of excellence1 is the strongest argument in favour of a preconceived plan40 ,now1 as in the organic world1 so in the inorganic1 it seems natural to view the chemical elements not as primordial1 but as the gradual outcome of a process of development1 possibly even of a struggle for existence4 ,but this evolution of the elements must have taken place at a period so remote as to be difficult to grasp by the imagination1 when our earth1 or rather the matter of which it consists1 was in a state very different from its present condition4 ,the epoch of elemental development1 remarks ,mr4 ,crookes1 is decidedly over1 and it may be observed that in the opinion of not a few biologists the epoch of organic development is verging upon its close4 ,is there then1 in the first place1 any direct evidence of the transmutation of any supposed 8element0 of our existing list into another1 or of its resolution into anything simpler8 ,to this question ,mr4 ,crookes answers in the negative4 ,we find ourselves thus driven to indirect evidence--to that which we may glean from the mutual relations of the elementary bodies4 ,first1 we may consider the conclusion arrived at by ,herschel1 and pursued by ,clerk-,maxwell1 that atoms bear the impress of manufactured articles4 8,a manufactured article may well be supposed to involve a manufacturer4 ,but it does something more3 it implies certainly a raw material1 and probably1 though not certainly1 the existence of by-products1 residues1 paraleipomena4 ,what or where is here the raw material8 ,can we detect any form of matter which bears to the chemical elements a relation like that of a raw material to the finished product1 like that1 say1 of coal-tar to alizarin8 ,or can we recognise any elementary bodies which seem like waste or refuse8 ,or are all the elements1 according to the common view1 co-equals8 ,to these questions no direct answers are forthcoming40 ,argument from ,prout's ,law4--,the bearing of the hypothesis of ,prout in relation to the evolution of the elements is first considered by ,mr4 ,crookes4 ,if that hypothesis were demonstrated it would show that the accepted elements are not co-equal1 but have been formed by a process of expansion or evolution4 ,according to this hypothesis the atomic weights of the elements are multiples by a series of whole numbers of the atomic weight of hydrogen4 ,it is true that accurate determinations of the atomic weights of different elements do not by any means harmonise with the values which ,prout's ,law requires2 nevertheless the agreement in so many cases is so close that one can scarcely regard the coincidence as accidental4 ,the atomic weights have been recalculated with extreme care by ,professor ,f4 ,w4 ,clarke1 of ,cincinnati1 and he says that 8none of the seeming exceptions are inexplicable4 ,in short1 admitting half-multiples as legitimate1 it is more probable that the few apparent exceptions are due to undetected constant errors than that the great number of close agreements should be merely accidental40 ,in reference to this suggestion of ,professor ,clarke1 ,mr4 ,crookes thinks that it places the matter upon an entirely new basis4 ,for1 suppose the unit atom to be not hydrogen1 but some element of still lower atomic weight1 say helium1 an element supposed by many authorities to exist in the sun and other stellar bodies--an element whose spectrum consists of a single ray1 and whose vapour possesses no absorbent power1 which indicates a remarkable simplicity of molecular constitution4 ,granting that helium exists1 all analogy points1 says ,mr4 ,crookes1 to its atomic weight being below that of hydrogen2 and here1 then1 we have the very element with atomic weight half that of hydrogen required by ,professor ,clarke as the basis of ,prout's ,law4 ,argument from the earth's crust4--,the probable compound nature of the chemical elements1 ,mr4 ,crookes thinks1 is better shown by a consideration of certain peculiarities in their occurrence in the earth's crust4 8,we do not10 he says1 8find them evenly distributed throughout the globe4 ,nor are they associated in accordance with their specific gravities3 the lighter elements placed on or near the surface1 and the heavier ones following serially deeper and deeper4 ,neither can we trace any distinct relation between local climate and mineral distribution4 ,and by no means can we say that elements are always or chiefly associated in nature in the order of their so-called chemical affinities3 those which have a strong tendency to form with each other definite chemical combinations being found together1 whilst those which have little or no such tendency exist apart4 ,we certainly find calcium as carbonate and sulphate1 sodium as chloride1 silver and lead as sulphides2 but why do we find certain groups of elements1 with little affinity for each other1 yet existing in juxtaposition or commixture80 ,as instances of such grouping he mentions nickel and cobalt2 the two groups of platinum metals2 and the so-called 8rare earths10 existing in gadolinite1 samarskite1 c4 ,why1 then1 are these elements so closely associated8 ,what agency has brought them together8 ,it cannot be considered that nickel and cobalt have been deposited in admixture by organic agency2 nor yet the groups of iridium1 osmium1 and platinum2 ruthenium1 rhodium1 and palladium4 ,these features1 ,mr4 ,crookes thinks1 seem to point to their formation severally from some common material placed in conditions in each case nearly identical4 ,argument from the compound radicals4--,a strong argument in favour of the compound nature of the elements1 ,mr4 ,crookes thinks1 is derived from a consideration of their analogy to the compound radicals1 or pseudo-elements as they might be called4 ,it may be fairly held that if a body known to be compound is found behaving as an element1 this fact lends plausibility to the supposition that the elements are not absolutely simple4 ,from a comparison of the physical properties of inorganic with those of organic compounds1 ,dr4 ,carnelley concluded that the elements1 as a whole1 are analogous to the hydrocarbon radicals4 ,this conclusion1 if true1 he added1 should lead to the further inference that the so-called elements are not truly elementary1 but are made up of at least two absolute elements1 which he named provisionally ,a and ,b4 ,in ,dr4 ,carnelley's scheme all the chemical elements save hydrogen are supposed to be composed of two simpler elements1 ,a #ab and ,b #b4 ,of these he regards ,a as a tetrad identical with carbon1 and ,b as a monad of negative weight2 perhaps the ethereal fluid of space4 ,his three primary elements are1 therefore1 carbon1 hydrogen1 and the ether4 ,argument from polymerisation4--,the polymeristic theory of the genesis of the chemical elements propounded by ,dr4 ,mills falls next to be considered4 ,it has been suggested by ,dr4 ,e4 ,j4 ,mills that the pristine matter was once in an intensely heated condition1 and that it has reached its present state by a process of free cooling1 and that the elements1 as we now have them1 are the result of successive polymerisations4 ,chemical substances in cooling naturally increase in density1 and we sometimes observe that as the density increases there are critical points corresponding to the formation of new and well-defined substances4 ,the bodies thus formed are known as polymers4 ,from a study of the classification of the elements ,mr4 ,mills is of opinion that the only known polymers of the primitive matter are arsenic1 antimony1 and perhaps erbium and osmium4 ,argument from the ,periodic ,law4--,lastly a scheme of the origin of the elements1 suggested to ,mr4 ,crookes by consideration of ,professor ,reynolds's method of illustrating the periodic law of ,newlands1 is discussed4 ,it was pointed out by ,newlands that atomicity and other properties of some of the chemical elements depend on the order in which their atomic weights succeeded one another2 and when this law was extended by ,professor ,mendelejeff to all elements it was apparent that a mathematical relation exists between the elements4 ,this far-reaching law has been fruitful of results4 ,referring to ,professor ,reynolds's diagram illustrating the law1 ,mr4 ,crookes says3 8,the more ,i study the arrangement of this zigzag curve1 the more ,i am convinced that he who grasps the key will be permitted to unlock some of the deepest mysteries of creation4 ,let us imagine if it is possible to get a glimpse of a few of the secrets here hidden4 ,let us picture the very beginnings of time1 before geological ages1 before the earth was thrown off from the central nucleus of molten fluid1 before even the sun himself had consolidated from the original protyle4#gd ,let us still imagine that at this primal stage all was in an ultra-gaseous state1 at a temperature inconceivably hotter than anything now existing in the visible universe2 so high1 indeed1 that the chemical atoms could not yet have been formed1 being still far above their dissociation-point4 ,in so far as protyle is capable of radiating or reflecting light1 this vast sea of incandescent mist1 to an astronomer in a distant star1 might have appeared as a nebula1 showing in the spectroscope a few isolated lines1 forecasts of hydrogen1 carbon1 and nitrogen spectra4 ,footnote #gd3 ,protyle is the term adopted by ,mr4 ,crookes to designate the original primal matter existing before the evolution of the chemical elements1 and out of which they were evolved4 ,protyle in chemistry is analogous to protoplasm in biology1 with this difference1 however1 that protyle is as yet hypothetical1 whereas protoplasm is known to be real4 8,but in course of time some process akin to cooling1 probably internal1 reduces the temperature of the cosmic protyle to a point at which the first step in granulation takes place2 matter as we know it comes into existence1 and atoms are formed4 ,as soon as an atom is formed out of protyle it is a store of energy1 potential 7from its tendency to coalesce with other atoms by gravitation or chemically7 and kinetic 7from its internal motions74 ,to obtain this energy1 the neighbouring protyle must be refrigerated by it1 and thereby the subsequent formation of other atoms will be accelerated4 ,but with atomic matter the various forms of energy which require matter to render them evident begin to act2 and1 amongst others1 that form of energy which has for one of its factors what we now call atomic weight4 ,let us assume that the elementary protyle contains within itself the potentiality of every possible combining proportion or atomic weight4 ,let it be granted that the whole of our known elements were not at this epoch simultaneously created4 ,the easiest formed element1 the one most nearly allied to the protyle in simplicity1 is first born4 ,hydrogen--or shall we say helium8--of all the known elements the one of simplest structure and lowest atomic weight1 is the first to come into being4 ,for some time hydrogen would be the only form of matter 7as we know it7 in existence1 and between hydrogen and the next formed element there would be a considerable gap in time1 during the latter part of which the element next in order of simplicity would be slowly approaching its birth-point3 pending this period we may suppose that the evolutionary process1 which soon was to determine the birth of a new element1 would also determine its atomic weight1 its affinities1 and its chemical position40 ,professor ,f4 ,w4 ,clarke on the pre-nebular condition of matter4--,views on elemental evolution almost similar to those of ,mr4 ,crookes's have been advocated by ,professor ,clarke4 ,spectroscopic phenomena1 says ,professor ,clarke1 are quite in harmony with the idea that all matter is at bottom one1 our supposed atoms being really various aggregations of the same fundamental unit4 8,everybody knows that the nebular hypothesis1 as it is to-day1 draws its strongest support from spectroscopic facts4 ,there shine the nebul in the heavens1 and the spectroscope tells us what they really are1 namely1 vast clouds of incandescent gas1 mainly1 if not entirely1 hydrogen and nitrogen4 ,if we attempt to trace the chain of evolution through which our planet is supposed to have grown1 we shall find the sky is full of intermediate forms4 ,the nebul themselves appear to be in various stages of development2 the fixed stars or suns differ widely in chemical constitution and in temperature2 our earth is most complex of all4 ,there are no #8missing links' such as the zoologist longs to discover when he tries to explain the origin of species4 ,first1 we have a nebula containing little more than hydrogen1 then a very hot star with calcium1 magnesium1 and one or two other metals added2 next comes a cooler sun in which free hydrogen is missing1 but whose chemical complexity is much increased2 at last we reach the true planets with their multitudes of material forms4 ,could there well be a more straightforward story8 ,could the unity of creation receive a much more ringing emphasis8 ,we see the evolution of planets from nebul still going on1 and parallel with it an evolution of higher from lower kinds of matter4 8,just here1 perhaps1 is the key to the whole subject4 ,if the elements are all in essence one1 how could their many forms originate save by a process of evolution upward8 ,how could their numerous relations with each other1 and their regular serial arrangements into groups1 be better explained8 ,in this1 as in other problems1 the hypothesis of evolution is the simplest1 most natural1 and best in accordance with facts40#ge ,footnote #ge3 ,popular ,science ,monthly for ,february #ahgf4 ,see also the ,january number for #ahgc4 ,dr4 ,g4 ,johnstone ,stoney on the pre-nebular condition of matter4--,further evidence that all the chemical elements were probably evolved from one common source1 is furnished by ,dr4 ,g4 ,johnstone ,stoney's 8,logarithmic ,law of ,atomic ,weights10 a theory recently advanced in a communication to the ,royal ,society4#gf ,a cardinal feature of this investigation is that in it atomic weights are represented by volumes1 not by lines4 ,a succession of spheres are taken whose volumes are proportional to the atomic weights1 and which may be called the atomic spheres4 ,when the radii of these spheres are plotted down on a diagram as ordinates1 and a series of integers as abscissas1 the general form of the logarithmic curve becomes apparent2 and close scrutiny has shown that either the logarithmic curve1 or some curve lying very close to it1 expresses the real law of nature4 ,footnote #gf3 ,proc4 ,roy4 ,soc4 for ,april #ai1 #ahhh1 p4 #aae4 ,if1 as seems probable1 the logarithmic law is the law of nature1 there appear to be three elements lighter than hydrogen1 which ,dr4 ,stoney has termed infra-fluorine1 infra-oxygen1 and infra-nitrogen4 ,and there are1 at all events1 six missing elements between hydrogen and lithium4 ,dr4 ,stoney's investigation is based on the fact that if the atomic weights of the chemical elements be arranged in order of magnitude1 periodic laws come to light1 viz43 those discovered by ,newlands1 ,mendelejeff1 and ,meyer4 ,from this it follows that there must be some law connecting the atomic weights with the successive terms of a numerical series--either alone or along with other variables4 8,this law10 says ,dr4 ,stoney1 8may be obtained in one of its graphical forms by plotting down a series of integers as abscissas1 and the successive atomic weights as ordinates4 ,in this way it furnishes a diagram which has somewhat the shape of a hurling-stick1 consisting of a short curved portion succeeded by a long and nearly straight portion4 ,but as this diagram cannot be directly identified with any known curve1 it does not suffice for the determination of the law4 8,the diagram1 however1 assumes a form which can be interpreted when we use the cube roots of the atomic weights for its ordinates1 instead of the atomic weights themselves4 ,this is equivalent to taking volumes instead of lines to represent the atomic weights4 ,when this is done1 the ends of the ordinates are found to lie near a regular and gradual curve1 from which they deviate to the right and left by displacements that are small and appear to follow periodic laws which have been in part traced4 ,the central curve is found on examination to be either a logarithmic curve or some curve lying exceedingly close to it4 ,if the curve be in reality the logarithmic curve1 it furnishes us the law that3 8,the cube root of the nth atomic weight log 7n q7 a small periodic correction2 where and q are constants1 the values of which are furnished by the observations4 8,either this logarithmic law1 or a law that lies exceedingly close to it1 must be the law of nature40 ,referring to this theory1 ,professor ,reynolds says3 8,it certainly introduced points of extraordinary importance1 though perhaps at present they could not all quite realise its fullest import4 ,there were several points of some little difficulty to be grappled with1 but it clearly pointed to the conclusion that we were fast approaching the time when physicists--both chemical and physicists proper--are combining to evolve out of the scientific work lying on the borderland most important and startling facts40 ,the bearing which ,dr4 ,stoney's conclusions1 like those of ,mr4 ,crookes1 have on the primitive condition of the material universe is obvious4 ,dr4 ,stoney1 like ,mr4 ,crookes1 considers that the chemical elements are subject to decay4 ,that they are not only generated but destroyed--that they are subject not only to evolution but dissolution4 ,he believes that the generative process probably takes place only at1 or beyond1 the confines of the universe1 and the destructive process at the centres of overgrown stars1 which is the position of lowest potential4 ,dr4 ,stoney thinks that this extinction of the chemical elements in the centre of a star is a cause which limits its size and prevents its overgrowth4 ,,the ,,impact ,,theory ,,in ,,relation ,,to ,,the ,,foregoing ,,theories ,,of ,,the ,,pre-,,nebular ,,condition ,,of ,,matter4 ,in all these theories1 as has already been observed1 the primitive condition of the universe was that of matter in a state of extreme tenuity1 while by aggregation the materials became successively larger and larger until they assumed the magnitude of suns and planets4 ,for example1 according to the meteoric theory1 meteorites are formed out of 8cosmical dust10 8fire-mist10 or condensed vapour1 and then suns and planets are formed by aggregation from these meteorites4 ,facts seem1 however1 to point to the very reverse as being the true course of events4 ,meteorites are undoubtedly the fragments of larger masses4 ,it looks more likely that they are1 as has already been stated1 fragments of stellar masses which have been shattered to pieces by collision1 and that this 8cosmical dust10 from which the meteorites are alleged to have been formed1 are simply the dust arising out of the destruction of the masses4 ,after the two bodies had collided and been shattered to pieces1 some of the fragments would undoubtedly be projected with a velocity that would carry them beyond the attractive power of the general mass1 and thus they would escape being volatilised4 ,these fragments would continue their wanderings through space as meteorites4 ,i cannot but think that the number1 as well as the importance1 of these wanderers has been greatly over-estimated4 ,mr4 ,lockyer states that ,dr4 ,schmidt1 of ,athens1 found that the mean hourly number of luminous meteors visible on a clear moonless night by one observer was fourteen4 ,certainly no such quantity is visible in this country4 ,in ,scotland1 at least1 one may often watch night after night under the most favourable conditions without having the good fortune to see a single meteor4 ,it is1 of course1 true that the immediately prior condition of a sun or a planet was that of matter in an extremely attenuated or dissociated state4 ,this is essential to the nebular1 as well as to the meteoric1 hypothesis4 ,but it is not with the immediately prior condition that we are at present concerned1 but with the primitive1 or pre-nebular1 condition4 ,take1 for example1 the case of the solar nebula1 out of which our sun and planets were formed4 ,was this nebulous mass formed from matter in a state of extreme tenuity1 scattered through space and collected together by gravity8 ,or did it result from two solid globes shattered to pieces by collision1 which were then converted into the nebulous condition by the heat generated from the collision8 ,it is no doubt true that the analogies of nature would1 at first sight1 be apt to lead us to the conclusion that the former theory was the more likely of the two1 as the larger is generally made by aggregation from the smaller4 ,but a little consideration will show that1 in the present case1 the weight of this analogy is more apparent than real4 ,the impact theory does not rest upon a purely hypothetical basis4 ,the cause to which it appeals has a real existence4 ,the point of uncertainty is whether the cause actually produces the effect which is attributed to it4 ,we know from observation that there are stellar masses1 some of them probably larger than our sun1 moving through space with enormous velocities in all directions4#gg ,according to the ordinary laws of chance1 collision at times would be an inevitable result1 and when such an event did take place the destruction of the colliding bodies1 and their consequent transformation into a nebulous mass1 would1 at least in many cases1 be a necessary result4 ,in fact1 we have1 in the case of these vast stellar masses1 what we know occurs among the invisible molecules of a gas4 ,so far as mere analogy is concerned1 the impact theory is just about as probable as the other4 ,footnote #gg3 ,the dark stellar masses which escape observation may be as numerous as those that are visible4 ,from what has been stated it would follow that in most cases the stellar masses have been formed out of the destruction of pre-existing masses1 like the geological formations out of the destruction of prior formations4 ,the theories do not account for the motion of the stars4--,according to all the foregoing theories aggregation and condensation are produced by gravity4 ,the materials dispersed throughout space are drawn together by their mutual attraction1 and aggregated round a centre of gravity4 ,gravitation1 although it imparts motion to the materials1 can impart no motion of translation to the mass itself4 ,gravitation cannot1 therefore1 be the cause of the motion of translation of the mass4 ,the stars are not supposed to be gravitating towards1 or around1 a great centre of attraction1 for they are found moving in straight lines in all directions1 which could not be the case if gravity were the cause of their motion4 ,to what cause is their motion1 therefore1 to be attributed8 ,a meteorite or other small body might be ejected from any system1 by the explosive force of heat or some other cause1 with a velocity which might carry it into boundless space2 but such could not be the case in regard to a body of the magnitude of a star4 ,no one for a moment could suppose that #ahcj ,groombridge1 for example1 moving at the rate of #bjj miles a second1 is an eject from any system4 ,according to the impact theory the whole is plain2 for this #bjj miles per second is simply a part of the untransformed motion of translation which the materials composing the star had from the beginning4 ,in other words1 the matter and the motion were eternal1 or1 what is more probable1 as will afterwards be seen1 co-existed from creation--not1 however1 as molecular motion1 but as motion of the mass4 ,the theories do not account for the amount of heat required4--,it has been shown that1 although the materials of our solar system had fallen together from an infinite distance1 it could not have generated heat sufficient to have formed a gaseous nebula extending to the distance of the planet ,neptune4 ,gravitation alone could not1 therefore1 have been the source from which the nebula obtained its heat4 ,the solar nebula1 however1 must originally have extended far beyond the orbit of ,neptune4 ,but supposing it could be demonstrated that the heat thus generated was sufficient to have formed a nebula extending to even twice the distance of ,neptune1 this would not remove the fatal objection to the gravitation theory of the origin of the solar nebula4 ,for the facts1 both of geology and of biology1 equally show that the sun has been radiating his heat at the present rate for more than twice the length of time that it could possibly have done had gravitation been the source from which the energy was derived4 ,this objection is alike fatal to the meteoric theory as it is to all other theories which attribute the origin and source of the heat to gravitation4 ,evolution of matter4--,our inquiries into stellar evolution do not1 however1 begin with the consideration of a gaseous nebula1 or with swarms of meteorites4 ,there was a pre-nebular evolution4 ,the researches of ,prout1 ,newlands1 ,mendelejeff1 ,meyer1 ,dumas1 ,clarke1 ,lockyer1 ,crookes1 ,brodie1 ,hunt1 ,graham1 ,deville1 ,berthelot1 ,stoney1 ,reynolds1 ,carnelley1 ,mills1 and others1 clearly show1 ,i think1 that the very matter forming this nebulous mass passed through a long anterior process of evolution4 ,and not only the matter1 but the very elements themselves constituting the matter1 were evolved out of some prior condition of substance4 ,i have already given at some length the views which have been advanced by several of our leading physicists and chemists on the evolution of the chemical elements1 and on some of the bearings which these views have on stellar evolution4 ,i shall now briefly refer to a point on which ,i venture to think the theory discussed in this volume seems to cast some additional light4 ,if the elements were evolved out of a common source1 there is1 in order to this1 one necessary condition1 viz4 an excessively high temperature2 for the temperature must be above the point of the dissociation of all the chemical elements4 8,in the primal stage of the universe10 says ,mr4 ,crookes1 8before matter1 as we now find it1 was formed from the protyle1 all was in an ultra-gaseous state1 at a temperature inconceivably hotter than anything now existing in the visible universe2 so high1 indeed1 that the chemical atoms could not yet have been formed1 being still far above their dissociation point40 ,what1 then1 produced this excessive temperature in this supposed ultra-gaseous protyle8 ,it could not have resulted from condensation by gravity4 ,in condensation the heat increases as the condensation proceeds1 because it is the condensation which produces the heat4 ,but here the reverse must have been the case1 for the ultra-gaseous mass was much hotter than the sun which was afterwards formed out of it4 ,it was1 according to ,mr4 ,crookes1 when this gaseous mass cooled down1 so as to permit of its becoming converted into solid matter1 that condensation into a sun could take place4 ,besides1 was it not the excessive heat which produced the assumed ultra-gaseous condition8 ,there is another difficulty besetting the theory that the primitive heat was derived from condensation by gravitation4 ,supposing we should assume it possible that the protyle could exist in this ultra-gaseous state without possessing temperature1 and that it obtained its heat from condensation by gravity1 then the fact of condensation taking place shows that the gas was not in a state of equilibrium4 ,but the gas could not have remained stationary for a single moment without beginning to condense while in a condition of unstable equilibrium4 ,we must therefore conclude that the gas must have been in some other condition than the gaseous state prior to condensation4 ,the impact theory seems to remove all these difficulties4 ,it is just as likely priori1 if not more so1 that the primitive form of the protyle should have been that of large cold masses moving through space in all directions1 with excessive velocities1 as that it should have been that of a gaseous mass in a state of unstable equilibrium4 ,if we assume the former condition1 then the colliding of these masses would account not only for the ultra-gaseous state1 but also for its inconceivably high temperature4 ,besides1 in this case we are not called upon to account for any other antecedent state of the masses before collision1 for they may have existed from the beginning of creation in the form of masses in motion through space4 ,had space and time permitted1 it might have been shown that there are other obscure points on which the theory seems to shed additional light4 ,i shall now1 in conclusion1 refer to a point wherein the theory differs radically from that of all other theories of stellar evolution4 ,but before doing so ,i may briefly refer to an objection which has been frequently urged against the theory4 ,objection considered4--,the objection to which ,i refer is this1 that1 had the nebul been produced by impact in the way implied in the theory1 then we ought to have had some historical record of such an event4 ,i can perceive no force in such an objection4 ,our historical records1 ,i presume1 do not extend much farther back than about #c1jjj years1 and we have no evidence to conclude that a new nebula makes its appearance in the visible firmament with such frequency2 and supposing it did1 we have no grounds for assuming that its production by impact in the way supposed by the theory would attract general notice4 ,it is doubtful if the nebula produced would1 in the first instance1 be actually visible4 ,i have shown that the temperature of the nebula could not have been less than about #cjj1jjj1jjj ,c41 and it is very doubtful if the gaseous mass enveloping all that was solid in the nebula would1 at such a temperature1 be self-luminous4 ,the probability is that all the chemical elements composing it would be in a state of utter dissociation1 and converted back into the original protyle from which they were derived1 again to be slowly reconverted into their former atomic condition as the temperature fell4 ,can we on scientific grounds trace back the evolution of the universe to an absolute first condition8--,as has been repeatedly stated1 all inquiries into the evolutionary history of the stellar universe begin in the middle of a process4 ,evolution is a process4 ,the changes that now occur arose out of preceding changes1 and these1 preceding changes out of changes still prior1 and so on indefinitely back into the unknown past4 ,this chain of causation--this succession of change--of consequent and antecedent--could not in this manner have extended back to infinity1 or else the present stage of the universe's evolution ought to have been reached infinite ages ago4 ,the evolution of things must therefore have had a beginning in time4 ,professor ,winchell1 in his final generalisation to his work1 8,world ,life10 has stated this matter so clearly and forcibly that ,i cannot do better than here quote his words on the subject4 8,we have not10 says ,professor ,winchell1 8the slightest scientific grounds for assuming that matter existed in a certain condition from all eternity1 and only began undergoing its changes a few millions or billions of years ago4 ,the essential activity of the powers ascribed to it forbids the thought4 ,for all that we know--and1 indeed1 as the conclusion from all that we know--primal matter began its progressive changes on the morning of its existence4 ,as1 therefore1 the series of changes is demonstrably finite1 the lifetime of matter itself is necessarily finite4 ,there is no real refuge from this conclusion2 for1 if we suppose the beginning of the present cycle to have been only a restitution of an older order effected by the operations of natural causes1 and suppose--what science is unable to comprehend--that older order to be a similar re-inauguration1 and so on indefinitely through the past1 we only postpone the predication of an absolute beginning1 since1 by all the admissions of modern scientific philosophy1 it is a necessity of nature to run down40 ,these are consequences which necessarily follow from every theory of stellar evolution which has hitherto been advanced4 ,the impact theory1 however1 completely removes the difficulty1 for according to it the evolutionary process can1 on purely scientific grounds1 be traced back to an absolute beginning in time4 ,if huge solid masses moving through space were the original condition of the universe1 then1 in so far as either philosophy or science can demonstrate to the contrary1 it might have been in this condition from all eternity4 ,we are therefore not called upon to account for this primitive condition of things4 ,now it is evident1 unless a collision should take place1 the universe would remain in this condition for ever3 without a collision there could be no change1 no work performed1 and absolutely no loss or gain of energy1 and therefore no process of evolution4 ,the first collision would be the absolute commencement of evolution--the beginning of the process of the development of the universe4 ,evolution would1 in this case1 have its absolute beginning in time1 and consequently was not eternal4 ,if1 on the other hand1 we assume1 what is far more in harmony with physics1 metaphysics1 and common sense1 that the universe was created in time1 we are still led to the same result as to an absolute commencement of evolution4 ,in both cases we reach a point beyond which there can be no legitimate inquiry2 no further question which the scientists can reasonably ask4 ,we have no grounds to conclude that there is anything eternal1 except ,god1 ,time1 and ,space4 ,but if time and space be subjective1 as ,kant supposes1 and not modes pertaining to the existence of things in themselves1 then ,god alone was uncreated1 and of ,him and to ,him are all things4 ---------------------------------------- -------------------------------- ---------------------------------------- -------------------------------- ,,index4 ,aqui ,range1 ,utah1 fault in1 #eg ,arcturus1 motion of1 #af ,atmosphere1 universal1 #hb ,dr4 ,hunt on1 #hf ,mr4 ,mattieu ,williams on1 #hf ,atomic weights1 logarithmic law of1 #ajj ,atoms1 according to ,herschel and ,clerk-,maxwell1 manufactured articles1 #ib ,binary systems1 #cb ,dr4 ,johnstone ,stoney on1 #cc ,sir ,w4 ,thomson on1 #cc ,biology1 testimony of1 as to age of sun's heat1 #fe ,brodie1 ,sir ,b41 on the pre-nebular condition of matter1 #hd ,brown and ,dickson on sediment of the ,mississippi1 #dj ,carnelley1 ,dr41 argument from compound radicals1 #id ,cassiopei1 motion of1 #af ,centauri1 distance of1 #af ,chemical elements1 evolution of1 #hj ,clarke1 ,prof4 ,f4 ,w41 on atomic weights1 #ic on evolution of the chemical elements1 #hj1 #hi on the pre-nebular condition of matter1 #ih ,comets1 according to ,laplace1 strangers to our system1 #ag according to ,prof4 ,a4 ,winchell1 strangers to our system1 #ag ,m4 ,faye on origin of1 #ag probable origin of1 #ag ,compound radicals1 argument from1 #ie ,condensation in relation to nebul1 #bg the last condition of a nebula1 #cj ,cosmical dust and 8fire-mist10 #ha1 #ajb ,crookes1 ,mr4 ,w41 on the pre-nebular condition of matter1 #ij-ih on protyle1 #if #fa ,cygni1 motion of1 #af ,darwin1 ,mr4 ,charles1 on geological time1 #fg ,denudation1 age of the globe as represented by1 #fc1 #fd average rate of whole globe1 #dd evidence from faults as to rate of1 #ec ,dr4 ,a4 ,geikie on rate of1 #da glacial epochs in relation to1 #df1 #dg in ,colorado1 #eh in past ages not much greater than at present1 #dd method employed to estimate its rate1 #ci1 #dg ,mr4 ,a4 ,r4 ,wallace's method of estimating its rate1 #ea of ,bristol coal-fields1 #ei of ,mississippi basin1 ,sir ,charles ,lyell on1 #dd of ,pendle ,range1 #fj of ,pentlands1 #ei of river basins1 #da of ,south of ,scotland1 #ee of ,wales1 #ei ,prof4 ,haughton's method of estimating its rate1 #ej ,rotation of the earth in relation to1 #df the direct method of estimating its rate1 #eb time required to effect the amount of1 #fc ,dewar and ,liveing on dissociation of chemical elements1 #hc ,dissociation of chemical elements1 ,dr4 ,t4 ,sterry ,hunt on1 #hb1 #he of chemical elements1 ,m4 ,berthelot on1 #hc of chemical elements1 ,m4 ,deville on1 #hc of chemical elements1 ,mr4 ,lockyer on1 #hb of chemical elements1 ,profs4 ,liveing and ,dewar on1 #hc of chemical elements1 ,prof4 ,schuster on1 #hc of chemical elements1 ,sir ,b4 ,brodie on1 #hb1 #hd ,dumas1 ,m41 on essential unity of matter1 #hc ,earth's crust1 argument from1 #ic rotation1 its influence on denudation1 #df ,emmons1 ,mr4 ,s4 ,f41 on a fault in ,aqui ,range1 #eh ,energy existing as motion of stellar masses1 #c transformed by collision1 #c ,evolution1 can it be traced back to a first condition8 #aaj evidence of1 from the grouping of the stars1 #ha from smaller to larger aggregates of matter1 #ha of matter1 #ajg of the chemical elements1 #hj1 #ajg ,faults1 evidence of rate of denudation from1 #ec examples of1 #ed-fj 8,grand ,wash10 ,colorado1 #eh in ,east ,tennessee1 #eh in ,strathmore1 #ee ,faye1 ,m41 on origin of comets1 #ag ,gaseous condition essential to the nebular hypothesis1 #be state1 second condition of a nebula1 #bd ,geikie1 ,dr4 ,a41 on area of the globe1 #dh on denudation of the ,pentlands1 #ei on examples of enormous faults1 #ee on rate of denudation1 #da ,geological epochs of past ages1 misconceptions regarding1 #di ,geological time1 ,mr4 ,a4 ,r4 ,wallace on1 #fe time1 ,mr4 ,charles ,darwin on1 #ff time1 ,prof4 ,haeckel on1 #fg time1 ,prof4 ,huxley on1 #fe1 #ff time1 ,sir ,andrew ,c4 ,ramsay on1 #fg ,geology1 testimony of1 in regard to age of sun's heat1 #ci ,glacial epoch1 age of the earth as determined by1 #fd epochs1 influence on denudation1 #df ,gravitation does not account for the heat required1 #ajf does not account for motion of the stars1 #aje insufficient to account for heat of nebul1 #bg ,groombridge #ahcj1 motion of1 #ae not an eject1 #ajf ,prof4 ,newcomb on motion of1 #ae ,grove1 ,sir ,w4 ,r41 on the pre-nebular condition of matter1 #gh ,haeckel1 ,prof1 on geological time1 #fg ,haughton1 ,prof41 method of estimating rate of denudation1 #ej ,heat1 age of the sun's1 #cg ,helmholtz on age of sun's heat1 #ce ,huggins1 ,mr41 and ,dr4 ,miller on spectra of nebul with one nitrogen line1 #hd ,hull1 ,prof41 on denudation of ,pendle ,range1 #fj on examples of enormous faults1 #ed ,humphreys and ,abbot on sediment of the ,mississippi1 #dj ,hunt1 ,dr4 ,t41 on the pre-nebular condition of matter1 #he on universal atmosphere1 #hf ,huxley1 ,prof41 on geological time1 #fe1 #ff ,hypothesis1 value of1 #gj 8,impact ,theory10 why so called1 #b in relation to theories of pre-nebular condition of matter1 #ajb removes difficulties regarding origin of heat1 #ajh1 #aji ,indi1 motion of1 #af ,king1 ,mr4 ,clarence1 on the ,wahsatch ,fault1 #ei ,lalande #baahe1 motion of1 #af #babeh1 motion of1 #af ,laplace1 ,m41 on the heat of the solar nebula1 #cj ,lavoisier1 ,m41 on simpler forms of matter1 #hf ,lesley1 ,mr4 ,j4 ,p41 on a fault in the ,appalachians1 #eg on fault in ,east ,tennessee1 #eh ,liveing and ,dewar on dissociation of chemical elements1 #hc ,lockyer1 ,mr41 on arrangement of the planets according to density1 #be nebul with solid matter in a gaseous mass1 #bj ,lockyer1 ,mr41 on essential condition of solar nebul1 #be on hypothesis1 #gj on number of meteorites1 #ajc on outburst of stars1 #cc on 8sorting0 of the chemical elements1 #be ,lodge1 ,prof4 ,o41 on ethereal origin of matter1 #hg on the pre-nebular condition of matter1 #hg on vortex atoms1 #hh ,logarithmic law of atomic weights1 #ajj ,lyell1 ,sir ,charles1 on denudation of the ,mississippi basin1 #dd ,macvicar1 ,dr41 on ethereal origin of matter1 #hg ,matter not probably eternal1 #aab ,mendelejeff1 ,prof41 on ,periodic ,law1 #if ,meteorites1 number greatly exaggerated1 #ajc probable origin of1 #ab ,sir ,h4 ,roscoe on constitution of1 #ab ,sir ,w4 ,thomson on1 #ab ,mill1 ,mr4 ,j4 ,s41 on hypothesis1 #gj ,miller1 ,dr41 and ,mr4 ,huggins on spectra of nebul with one nitrogen line1 #hd ,mills1 ,dr41 on ,polymerisation1 #ie ,morris1 ,mr4 ,charles1 on the pre-nebular condition of matter1 #ge ,nebul1 broken fragments in a gaseous mass1 #ai cometic1 #bb condensation insufficient to account for heat of1 #bg ,nebul condensation1 last condition of1 #cj first condition of1 #ai gaseous state1 second condition of1 #bd globular1 #ba heat of1 not due to gravitation1 #bg how they occupy so much space1 #ah how origin of by impact might not have been observed1 #aaj must possess an excessive temperature1 #bf ,mr4 ,lockyer on1 #bj-bb origin of1 #ah ,prof4 ,a4 ,winchell on meteoric origin of1 #bb ,prof4 ,tait on1 #bj ,sir ,w4 ,thomson on origin of1 #f1 #bh spheroidal1 #bb why of such various shapes1 #ai ,nebular hypothesis1 gaseous condition essential to1 #b1 #e ,newcomb1 ,prof41 on motion of #ahcj ,groombridge1 #ae ,newlands on ,periodic ,law1 #if ,nova ,cygni1 on sudden outburst of1 #cc ,objection considered1 #aji ,palozoic times1 winds probably not higher than at present1 #df ,peach1 ,mr4 ,b4 ,n41 on examples of enormous faults1 #ee on denudation of the south of ,scotland1 #ee ,periodic ,law1 argument from1 #if ,prof4 ,mendelejeff on #if ,periodic ,law1 ,newlands on1 #if ,prof4 ,reynolds on1 #if ,planets1 on their arrangement according to density1 #be ,polymerisation1 argument from1 #ie ,dr4 ,mills on1 #ie ,pouillet1 on rate of solar radiation1 #b1 #ce ,powell1 ,major ,j4 ,w41 on denudation of ,uinta ,mountains1 #eh ,pre-nebular condition of matter1 ,dr4 ,g4 ,johnstone ,stoney on1 #ii condition of matter1 ,dr4 ,t4 ,sterry ,hunt on1 #he condition of matter1 ,mr4 ,charles ,morris on1 #ge condition of matter1 ,mr4 ,w4 ,crookes on1 #ij condition of matter1 ,prof4 ,a4 ,winchell on1 #ga condition of matter1 ,prof4 ,f4 ,w4 ,clarke on1 #ih condition of matter1 ,prof4 ,lodge on1 #hg condition of matter1 ,sir ,b4 ,brodie on1 #hd condition of matter1 ,sir ,w4 ,r4 ,grove on1 #gh evolution1 #ajg ,proctor1 ,r4 ,a41 on meteoric origin of solar system1 #bc ,protyle1 the primal matter1 #if ,prout's ,law1 argument from1 #ib ,ramsay1 ,sir ,andrew ,c1 on denudation of ,bristol coal-fields1 #ei on denudation of ,wales1 #ei on geological time1 #fg ,reynolds1 ,prof41 on ,periodic ,law #if ,rogers1 ,prof4 ,h4 ,d41 on a great fault in the ,appalachian coal-fields1 #eg ,roscoe1 ,sir ,h41 on constitution of meteorites1 #ab ,rotation1 supposed influence on denudation1 #df ,saigey1 ,m41 on ethereal origin of matter1 #hg ,schmidt1 ,dr41 on number of meteorites1 #ajc ,solar nebula1 ,m4 ,laplace on heat of1 #cj ,mr4 ,lockyer on condition essential to1 #be ,sir ,w4 ,thomson on1 #f1 #bh ,solar radiation1 rate of1 according to ,pouillet and ,langley1 #ce ,solar system1 ,mr4 ,r4 ,a4 ,proctor on meteoric origin of1 #bc ,star clusters1 #cd ,stars1 evidence of evolution from their grouping1 #ha how origin of by impact might not have been observed1 #aaj in four groups1 #ha motion not accounted for by gravitation1 #aje motion not due to their mutual attractions1 #ad motion of1 how in straight lines1 #ad sudden outbursts of1 #cc ,stoney1 ,dr4 ,g4 ,johnstone1 on the pre-nebular condition of matter1 #ii ,subarial denudation1 method of estimating rate of1 #ci1 #dg ,sun1 age of heat of1 #cd ,sun's heat1 age of1 according to ,geology1 #cg age of1 a crucial test1 #cd1 #cg ,sun's heat1 age of1 according to ,thomson and ,tait1 #ce age of1 as determined by ,biology1 #fd age of1 as determined by ,geology1 #ci ,tait1 ,prof41 nebul with solid matter in a gaseous mass1 #bj on age of sun's heat1 #ce ,temperature excessive1 essential to nebul1 #bf produced by collision1 #e ,thomson1 ,sir ,w41 on age of sun's heat1 #ce on meteorites1 #ab on origin of solar nebula1 #bh on solar nebula1 #f suggestion by1 #hf ,tides1 supposed influence on denudation1 #de ,tycho ,brahe1 on sudden outburst of a star1 #cc ,tylor1 ,alfred1 on the denudation of ,mississippi ,basin1 #dj ,uinta ,mountains1 denudation of1 #eh fault in1 #eg ,vortex atoms1 ,prof4 ,lodge on1 #hh 8,wahsatch ,fault10 ,utah1 immense dislocation1 #eh ,wallace1 ,mr4 ,a4 ,r41 on geological time1 #fe1 #fh method of estimating rate of denudation1 #eg ,williams1 ,mr4 ,mattieu1 on universal atmosphere1 #hf ,winchell1 ,prof4 ,a41 on age of the earth1 #fd on comets strangers to our system1 #ag on denudation of ,colorado plateau1 #eh on deposition of ,palozoic sediment1 #de on ethereal medium1 #hg on meteoric origin of nebul1 #bb on nebular hypothesis1 #fi on the pre-nebular condition of matter1 #ga ---------------------------------------- -------------------------------- ,d4 ,,appleton ,,co4',s ,,publications4 ,,discussions ,,on ,,climate ,,and ,,cosmology4 ,by ,,james ,,croll1 ,,ll4 ,d41 ,f4 ,r4 ,s4 ,with ,chart4 #abmo4 ,cloth1 #b4jj4 ,,contents3 ,misapprehensions regarding the ,physical ,theory of ,secular ,changes of ,climate4--,the ,ice of ,greenland and the ,antarctic ,continent not due to ,elevation of the ,land4--,mr4 ,alfred ,r4 ,wallace's ,modification of the ,physical ,theory or ,secular ,changes of ,climate4--,the ,physical ,cause of ,mild ,polar ,climates4--,interglacial ,periods and ,distribution of ,flora and ,fauna in ,arctic ,regions4--,temperature of ,space and its ,bearing on ,terrestrial ,physics4--,probable ,origin and ,age of the ,sun's ,heat1 etc41 etc4 ,,climate ,,and ,,time ,,in ,,their ,,geological ,,relations3 ,a ,,theory ,,of ,,secular ,,changes ,,of ,,the ,,earth',s ,,climate4 ,by ,,james ,,croll1 of ,h4 ,m4 ,geological ,survey of ,scotland4 ,with ,maps and ,illustrations4 #abmo4 ,cloth1 #b4ej4 8,i have studiously avoided introducing anything of a hypothetical character4 ,all the conclusions are based on known facts or admitted physical principles4 ,in short1 the aim of the work is to prove that secular changes of climate follow1 as a necessary effect1 from admitted physical agencies1 and that these changes1 in as far as the past climatic condition of the globe is concerned1 fully meet the demand of the geologist40--,from the ,preface4 ,,other ,,worlds ,,than ,,ours3 ,,the ,,plurality ,,of ,,worlds1 ,,studied ,,under ,,the ,,light ,,of ,,recent ,,scientific ,,researches4 ,by ,,richard ,,anthony ,,proctor4 ,with ,illustrations1 some colored4 #abmo4 ,cloth1 #b4ej4 ,,light ,,science ,,for ,,leisure ,,hours4 ,a ,series of ,familiar ,essays on ,scientific ,subjects1 ,natural ,phenomena1 etc4 ,by ,,richard ,,anthony ,,proctor4 #abmo4 ,cloth1 #a4ge4 ,,the ,,moon3 ,,her ,,motions1 ,,aspect1 ,,scenery1 ,,and ,,physical ,,conditions4 ,with ,three ,lunar ,photographs1 and many ,plates1 ,charts1 etc4 ,by ,,richard ,,anthony ,,proctor4 #hvo4 ,cloth1 #c4ej4 ,,the ,,expanse ,,of ,,heaven4 ,a ,series of ,essays on the ,wonders of the ,firmament4 ,by ,,richard ,,anthony ,,proctor4 #abmo4 ,cloth1 #b4jj4 ,,our ,,place ,,among ,,infinities4 ,a ,series of ,essays contrasting our ,little ,abode in ,space and ,time with the ,infinities around us4 ,to which are added ,essays on the ,jewish ,sabbath and ,astrology4 ,by ,,richard ,,anthony ,,proctor4 #abmo4 ,cloth1 #a4ge4 ,,physical ,,expression3 ,its ,modes and ,principles4 ,by ,,francis ,,warner1 ,m4 ,d41 ,assistant ,physician1 and ,lecturer on ,botany1 to the ,london ,hospital1 etc4 ,with #ea ,illustrations4 #abmo4 ,cloth1 #a4ge4 8,in the term #8,physical ,expression1' ,dr4 ,warner included all those changes of form and feature occurring in the body which may be interpreted as evidences of mental action4 ,at first thought it would seem that facial expression is the most important of these outward signs of inner processes2 but a little observation will convince one that the posture assumed by the body--the poise of the head and the position of the hands--as well as the many alternations of color and of general nutrition1 are just as striking evidences of the course of thought4 ,the subject thus developed by the author becomes quite extensive1 and is exceedingly interesting4 ,the work is fully up to the standard maintained in #8,the ,international ,scientific ,series4'0--,science4 8,among those1 besides physicians1 dentists1 and oculists1 to whom ,dr4 ,warner's book will be of benefit are actors and artists4 ,the art of gesticulation and of postures is dealt with clearly from the scientific student's point of view4 ,in the chapters concerning expression in the head1 expression in the face1 expression in the eyes1 and in that on art criticism1 the reader may find many new suggestions40--,philadelphia ,press4 ,,common ,,sense ,,of ,,the ,,exact ,,sciences4 ,by the late ,,william ,,kingdon ,,clifford4 ,with #ajj ,figures4 #abmo4 ,cloth1 #a4ej4 8,this is one of the volumes of #8,the ,international ,scientific ,series1' and was originally planned by ,mr4 ,clifford2 but upon his death in #ahgi the revision and completion of the work were intrusted to ,mr4 ,c4 ,r4 ,rowe4 ,he also died before accomplishing his purpose1 and the book had to be finished by a third person4 ,it is divided into five chapters1 treating number1 space1 quantity1 position1 and motion1 respectively4 ,each of these chapters is subdivided into sections1 explaining in detail the principles underlying each4 ,the whole volume is written in a masterful1 scholarly manner1 and the theories are illustrated by one hundred carefully prepared figures4 ,to teachers especially is this volume valuable2 and it is worthy of the most careful study40--,new ,york ,school ,journal4 ,,jelly-,,fish1 ,,star-,,fish1 ,,and ,,sea-,,urchins4 ,being a ,research on ,primitive ,nervous ,systems4 ,by ,g4 ,j4 ,,romanes1 ,f4 ,r4 ,s41 author of 8,mental ,evolution in ,animals10 etc4 #abmo4 ,cloth1 #a4ge4 8,a profound research into the laws of primitive nervous systems conducted by one of the ablest ,english investigators4 ,mr4 ,romanes set up a tent on the beach and examined his beautiful pets for six summers in succession4 ,such patient and loving work has borne its fruits in a monograph which leaves nothing to be said about jelly-fish1 star-fish1 and sea-urchins4 ,every one who has studied the lowest forms of life on the sea-shore admires these objects4 ,but few have any idea of the exquisite delicacy of their structure and their nice adaptation to their place in nature4 ,mr4 ,romanes brings out the subtile beauties of the rudimentary organisms1 and shows the resemblances they bear to the higher types of creation4 ,his explanations are made more clear by a large number of illustrations4 ,while the book is well adapted for popular reading1 it is of special value to working physiologists40--,new ,york ,journal of ,commerce4 8,a most admirable treatise on primitive nervous systems4 ,the subject-matter is full of original investigations and experiments upon the animals mentioned as types of the lowest nervous developments40--,boston ,commercial ,bulletin4 ,new ,york3 ,d4 ,,appleton ,,co41 #a1 #c1 #e ,bond ,street4 ---------------------------------------- -------------------------------- ,transcriber's note3 ,front matter1 #8,by' changed from small caps to letter case1 8,by ,,james ,,croll1 ,,ll4,d41 ,f4,r4,s4 ,with0 ,page #b1 comma inserted after #8,mag41' 8,phil4 ,mag41 ,july #ahgh20 ,page #be1 full stop inserted after #8,lectures1' 8,manchester ,science ,lectures40 ,page #cg1 heading #8,testimony444' changed to small caps4 ,page #da1 #8years' inserted1 8,mean #c1cgh years0 ,page #ed1 full stop inserted after #8,mem41' 8,mem4 ,geol4 ,survey of ,lancashire0 ,page #ei1 full stop inserted after #8vol4 i41' 8,memoirs of ,geol4 ,survey1 vol4 i40 ,page #aac1 #8radicles' changed to #8radicals1' 8argument from compound radicals0 ,page #aae1 ditto inserted1 8 on examples of enormous faults0 ,page #aaf1 ditto inserted1 8 globular0 ,page #aag1 page entries reversed1 8of solar radiation1 #b1 #ce0 ,page #aag1 #8geologica' changed to #8geological1' 8on geological time0 ,page #aah1 ditto inserted1 8 fault in1 #eg0