" contained seed; the nutritive quality | boundary line sharply round its true of wheat is essential to securing the domain ; and he professes that it is early development of the germ; and as much for the sake of science as for "the labor of every earth-worm" is the sake of religion that he has pubprimarily of benefit to the earth-worm lished his criticism. Now, it was itself. But before my statement can precisely for this very purpose of be shown to be "reckless," Dr. Con- "drawing the boundary line sharply der must point at least to some one round the true domain of science, instance, either in the vegetable or ani- that I discussed the subject of mal kingdom, of a structure or property natural theology at all. In the past presented by one species, which is of this boundary line has been encroachno apparent benefit to that species, but ed upon by the forces of transcenwhich is of obvious benefit to some dental dogma, and this 80 seriother. And I am in no fear that ously to the detriment of science he will be able to do this, because the that all who wish well to her challenge has virtually been before future progress should be instant, in the world of naturalists ever since the season and out of season, to clear from time when Mr.-Darwin wrote that, if her path the obstructions raised by one such case could be pointed to, it supernatural hypotheses in general, would be destructive of his whole and by the doctrine of final causes in theory. particular. Without going into the Without waiting to follow Dr. history of the subject, it is a matter Conder into those of his criticisms of notoriety that science has been which are directed against the theory more hampered by such hypotheses of Natural Selection itself, as distin- and doctrines than by hypotheses and guished from my method of render- doctrines of any other kind; and ing the evidence, I shall conclude by briefly explaining the reason why, in rendering this evidence, I was led to touch upon the relation of Natural Science to Natural Theology. therefore, in the interests of science, the boundary line should be drawn round its "true domain," by insisting on the essentially distinct character of Natural Science and Natural TheoDr. Conder says: "Cultivators of logy as separate departments of huprofessors and amateurs man thought. Thus only can the alike are doing not a little to true educational value of natural loosen its authority, and especially to science be maintained, and thus only imperil if not destroy its educa ion- can the permanent interests of Natual value, by neglecting to draw the ral Theology be promoted. science AUTHOR OF "THE FUEL OF THE SUN," THROUGH NORWAY WITH A KNAPSACK," "A SIMPLE PREFACE. I AM NOT AWARE that this reprint of some of my scattered notes and essays demands any apology. The practice of making such collections and selections by the author himself has now become ve y general, and is much better done thus than by friends after his death. Besides this, it supplies a growing want of these busy times, when so many of us are prevented by the struggles of business from sitting down to the consecutive systematic study of a formal treatise. I hav: kept this demand steadily in view throughout, by selecting subjects which are likely to be interesting to all readers who are sufficiently intelligent to prefer sober fact to. sensational fiction, but who, at the same time, do not profess to be scientific specialists. In the writing of these papers, my highest literary ambition has always been to combine clearness nd simplicity with some attempt at philosophy. WILLESDEN, September, 1882. W. M. W. 1. THE FUEL OF THE SUN. ventured to grapple with the argument it contains, although every possible opportunity and provocation for doing so is designedly afforded. It all rests upon the question which is discussed in the first three chapters, viz., Whether the atmosphere which sur rounds our earth is limited or unlimited in extent? If my reasoning upon this funda mental question is refuted, all that follows. necessarily falls to the ground. If I am right, all our standard treatises on pneumat ics and meteorology, which repeat the argue The book has been handled in a most ments contained in Dr. Wollaston's cele courteous and indulgent spirit by all the re-brated paper, must be remodeled. At the viewers who have noticed it, but none have putset, I reprint that paper, and point out a I offer the following sketch of the main argument which is worked out more fully in the essay published in January, 1870, under the above title, hoping that many who hesitate to plunge into a presumptuous speculative work of more than 200 octavo pages, may read this article, and reflect upon the subject. very curious and monstrous fallacy which, for half a century, remained undetected, and had been continually repeated. 5. The forces which upheave the solar prominences. 6. The origin of the corona and zodiacal light. As the main point of issue between myself and Dr. Wollaston is merely a question of very simple arithmetic and geometry, nothing can be easier than to set me right if I am wrorg; and, as the philosophic consequences depending upon this issue are of vast and fundamental importance, the question cannot be ignored by those who stand before the world as scientific authorities, without a practical abdication of their philosophical re-and its connection with solar activity. sponsibilities. Any man who publishes an astronomical or meteorological treatise without discussing this question, which stands before him at the threshold of his subject, is unfit for the task he has undertaken, and unworthy of public confidence. This may appear a strong conclusion just now, but a few years will be sufficient to graft it firmly into the growth of scientific public opinion.* 7. The origin of the meteorites and the asteroids. 8. The meteorological phenomena of the planets. 8. The origin of the rings of Saturn. 10. The origin of the special structure of the nebulæ. II. The source of terrestrial magnetism, The first and second chapters are devoted to an examination of the limits of atmospheric expansibility. The experimental investigation of Dr. Andrews, Mr. Grove, Mr. Gassiot, and M. Geissler are cited to prove that the expansibility of the atmosphere is unlimited, and other cosmical evidence is adduced in support of this conclusion. As this, which is really the foundation of "The Fuel of the Sun" is simply an at- the whole argument, is directly opposed to tempt to trace some of the consequences the views expressed by Dr. Wollaston, in his which must of necessity result from the exist- celebrated paper on "The Finite Extent of ence of a universal atmosphere, and it dif- the Atmosphere," published in 1822, and fers from other attempts to explain the grea: generally accepted as established science, this solar mystery, by making no demands what-paper is reprinted in the second chapter, and ever upon the imagination, inventing nothing carefully examined. -no outside meteors, no new forces o: ma- Dr. Wollaston says "that air has been terials. It supposes nothing whatever to cx- rarefied so as to sustain 1-100th of an inch of ist but the known facts of the laboratory-barometrical pressure,' and further, that the familiar materials of the earth and its at- 'beyond this limit we are left to conjectures mosphere. It is shown that these materials founded on the supposed divisibility of matand the forces residing within them must of ter; if this be infinite, so also must be the necessity produce a sun, and manifest eter-extent of our atmosphere." nally all the observed solar phenomena, pro- I contend that our knowledge of the whole vided only they are aggregated in the quan- subject is fundamentally altered since these tities which our own central luminary pre-words were written, We are no longer sents, and are surrounded by attendant planets such as his. Nothing is assumed or taken for granted beyond the simple fundamental hypothesis that the laws of nature are uniform throughout the universe. The argument thus conducted leads us step by step to a natural and connected explanation of the following important phenomena : I. The sources of solar and stellar heat and light. 2. The means by which the present amount of solar heat and light must be maintained so long as the solar system continues in exist ence. 3. The origin of the general and particular phenomena of the sun-spots. 4. The cause of the varying splendor of the photosphere, including such details as the "faculæ," "mottling,' 'granulations," etc. “left to conjectures founded on the supposed divisibility of matter" to determine the possibility of further expansibility than that indicated by 1-100th of an inch of barometrical pressure as we now have means of obtaining ten times, a hundred times, a thousand times, or even an infinitely greater rarefaction than Wollaston's supposed limit, an apparently absolute vacuum being now attainable; and although the transmission of electricity affords a means of testing the existence of atmospheric matter with a degree of delicacy of which Wollaston had no conception, we are still unable to detect any indication of any limit to its expansibility. The most remarkable part of Dr. Wollas ton's paper is the reductio ad obsurdum by which he seeks to finally demonstrate the finite extent of our atmosphere. lle maintains, as I do, that if the elasticity of our atUp to the present date (1882) nobody, as far as I mosphere is unlimited, its extension must be know, has questioned my figures or defended those commensurate with the universe, that every of Wollaston. Sir William Grove has written to orb in space will, by gravitation, gather me, pointing out his own anticipations of my conclusions respecting the universality of atmospheric mat-around itself an atmosphere proportionate to ter. Sir Charles Lyell, before his death, expressed its gravitating power, and that, by taking the very strong approval of my conclusions, and many known quantity of the earth's atmosphere To expect any immediate, unreserved adoption of as our unit, we may calculate the amount of Bach bold speculations would be unreasonable. atmosphere possessed by any heavenly body other men of scientific eminence have done the same. of which the mass is known. On this basis Dr. Wollaston calculates the atmosphere of the sun, and concludes that its extent will be so great as to visibly affect the apparent motions of Mercury and Venus, when their declination makes its nearest approach to that of the sun. No such disturbance being actually observable, he concludes that such an atmosphere as he has calculated cannot exist. In like manner he calculates the atmosphere of Jupi er, and finds it to be so great, that its refraction would be sufficient "to render the fourth satellite visible to us when behind the center of the planet, and consequently to make it appear on both (or all) sides at the same time.' its known quantity of atmospheric envelope as units, and calculating, by the simple rule I have laid down in opposition to Wollaston's, I find that the total weight of the sun's atmosphere should be at least 117,681,623 times that of the earth's, and the pressure at its base equal, at least, to 15,233 atmospheres. What must be the results of such an atmospheric accumulation? The experiment of compressing air in the condensing syringe, and thereby lighting a piece of German tinder, is familiar to all who have studied even the rudiments of physical science. Taking the formula of Leslie and Dalton, and applying them to the solar pressure of 15.233 atmospheres, we arrive, On examining these calculations, I have according to Leslie, at the inconceivable discovered the very curious error above re- temperature of 380,832° C., or 685,529° F., ferred to. As this is a matter of figures that as that due to this amount of compression, cannot be abridged, I must refer the reader or, according to Dalton, at 761,665° F. What to the original calculations. I will here will be the effects of such a degree of heat merely state that Wollaston's method of cal-upon materials similar to those of which our culating the solar gravitation atmosphere and that of Jupiter and the moon leads to the monstrous conclusion that, in ascending from the surface of the given orb, we always have the same limited amount of atmospheric matter above as that with which we started, although we are continually leaving a portion of it below. Wollaston's mistake is based on the assumption that, under the circumstances supposed, the atmospheric pressure and density, at any given distance from the center of the given o.b, will vary inversely with the square of that distance. As the area of the base upon which such pressure is exerted varies directly with the square of the distance, the total atmosphere above every imaginable starting-distance wonld thus be ever the same. earth is composed? Let us first take the case of water, which, for reasons I have stated, should be regarded as atmospheric, or universally diffused matter. This brings as to a subject of the highest and widest philosophical and practical importance. I refer to the antagonism between the force of heat and that of chemical combination, to which the French chemists have given the name "dissociation." Having myself been unable to find any satisfactory English account of this subject at a time when it had already been well treated by French and German authors, in the form of published lectures and cyclopædia articles, I assume that others may have encountered a similar difficulty, and therefore dwell rather more fully upon this part of my present summary. That this assumption, so utterly at variance with the known laws of atmospheric distribution, should have remained unchallenged for half a century, and that the conclusions based upon it should be accepted by the whole scientific world, and repeated in standard treatises, such as those of the "Encyclopedia Britannica," etc., etc., is, I think, one of the most remarkable curiosities presented by the history of science. If it were merely a little cobweb in some obscure corner There appears to be a remarkable analogy of philosophy, there would be nothing sur-between dissociation and evaporation. When prising in its escape from the besom of scientific criticism; but this is so far from being the case, that it has hung, since 1822, like a dark vail obscuring another, a wider, and more interesting view of the universe which the idea of a universal atmosphere opens out. But I must now proceed to the next stage of the argument. It appears that all chemical compounds may be decomposed by heat, and that, at a given pressure, there is a definite and special temperature at which the decomposition of each compound is effected. For the absolute and final establishment of the universality of this law further investigations are necessary, actual investigations having established it as far as they have gone, but these have not been exhaustive. Starting from the conclusion reached in the previous chapters, that the atmosphere of our earth is but a portion of a universal elastic medium which it has attached to itself by its gravitation, and that all the other orbs of space must, in like manner, have obtained their proportion, I take the earth's mass, and a liquid is vaporized, a certain amount of heat is "rendered latent," and this quantity varies with the liquid and with the pressure, but is definite and invariable for each liquid at a given pressure. In like manner, when a compound is dissociated, a certain amount of heat is "rendered latent," or converted into dissociating force, and this varies with each compound and with the pressure, but is definite and invariable for each compound at a given pressure. Further, when condensation occurs, an amount of heat is evolved, as temperature, exactly equal to that which was rendered latent in the evaporation of the same substance under the same pressure; and, in |