first article in the Geological Magazine for 1865, from which I have already quoted, in asking the question, "Have we got back to the first of earth's created beings?" and replying "That is not for us to say," concludes his remarks with these words: "Judging from analogy, then, the Eozoön rock of Canada was the foraminiferous formation in one part of an ocean which elsewhere may have borne manifold and higher species, and buried them in sands and muds, that have since lost all form and feature by the metamorphism of age and pressure, or which were altogether shorn away by wave and weather when the old ocean-bed was lifted up."* Nothing can be more evident than that language such as this expresses bewilderment in fundamental thought, such as prepares men for any change. The theory of progression, as it has been called, is sick and ready to die. That is, not merely Darwin's notion of the transmutation of species, but the theory of a gradual evolution of higher forms, either by creations or transmutations. The grand, general idea, that the production of man formed the last step in an inconceivably long chain of development, which rose from a low first link fastened on somewhere to a piece of "fundamental granite," is expiring! If "manifold and higher species" might live in the ocean at the time of the Eozoön, why might not manifold and higher species live also on land? And if higher species, why not the highest? Here we ask our guide, if he knows the road beyond? and he replies, "No, gentlemen, we are off the track. I see no path either behind or ahead!" Such is Geological Science in one of its grandest features at the present hour. Pressed to speak as to even the way to light, it can tell us simply nothing. So we must think for ourselves.

If, then, we give up the merely vertical movement of upheaval and subsidence, with latitude maintained, and believe that since half an English county could be turned over like a turf on its grassy side, any number of such formations could be pushed along from tropical to temperate and thence to arctic positions on the great globe, we have, at least, one line of thought marked off, by which changes of climate, and all consequent changes of species, may ultimately be accounted for. We have also that in view, of which the sickly theory of progression, as it has been held by geologists, may be allowed to die, and the doctrine of creation, as taught us through Moses, may be seen in its proper scientific light.

As a fuller illustration of what we mean, we must direct

*Geological Magazine, January, 1865, p. 3.

in

the most earnest attention to some of the very thoroughly ascertained facts of geology. We observe that Sir Charles Lyell says: "Mr. [now Dr.] Bowerbank, in a valuable publication on the fossil fruits and seeds of the island of Sheppey, near London, has described no less than thirteen fruits of palms of the recent type Nipa, now only found in the Molucca and Philippine Islands, and in Bengal." He says also, that "the teeth and bones of crocodiles and turtles " are found here, with other relics of an unquestionably tropical character. Here then fairly occurs the question as to whether all these undoubtedly tropical productions and living creatures grew the present latitude of London; or have the relics of a truly tropical situation been transported northward by the removal of the strata in which they were entombed? Certain minor causes might, perhaps, account adequately for a milder climate prevailing in England, or in its latitude, than even that which is produced by the Gulf-stream now. But it is impossible, apart from the vertical rays of a tropical sun, to account for the richest results of a tropical clime; and the very richest are entombed in the London clay. Is it not evident that this clay was formed within the tropics, and that somehow it has been removed, until it lies in our northern latitude? And is it not this removal alone that can account for the difference between its climatal character and that of the beds of sediment now forming in the Thames? But if such is the account to be given of changes in climate, we must recast our ideas of the extinction of species, and alter our views of what is called geological time. The shutting off of the warm waters of the great Atlantic current from our shores might bring a glacial period over Britain; but as we know, the letting on of those waters would not give us the heat of Bengal. No raising or sinking of the surface, which could be conceived, could give us the effects of the direct radiance of a tropical sun without those rays themselves. But the removal of the abodes of tropical creatures from under tropical skies is abundantly sufficient to account for their extinction or emigration from the portion of the earth's surface so removed; and it requires only, that we should be able to form some true idea of the time consumed in this removal, in order to our coming somewhat near the date of the extinctions and emigrations which the records of the rocks disclose.

It is at this point that we are, as it were, compelled to look into current astronomy, where that science has been called in to account for changes on the surface of the earth. And here, too, we must distinguish between practical and physical science. Because astronomers predict, to the fraction of a

second, when an eclipse will occur, if it should be thousands of years hence, it is taken for granted that all they teach must be true! But while a child may look to the dial of a timepiece, and tell us to a second when the pointer will cover a certain mark, not one among ten thousand of grown men can go behind the dial, and explain how the causes operate by which the hands or pointers are moved. So may a very poor thinker calculate the time of a transit, or an eclipse, while the loftiest intellect becomes bewildered, and is lost in trying to prove even the existence of those forces on the reality of which the fundamental doctrines of physical astronomy depend. The noblest minds are overtaxed when honestly attempting to tell us whether there is such a thing as centrifugal force, and what it really is, which is called "gravitation." No one has gone behind the scenes, and seen how the highest authorities in astronomy are situated, without seeing that the physics of this science are as unsettled and uncertain as those of geology itself. But we gladly look into its teachings

notwithstanding.

Mr. Croll, of the Glasgow Andersonian University, has presented the world of science with the best phase of one of the most interesting of all theories from this quarter.* Sir Charles Lyell has given Mr. Croll great credit for his labours in this matter, as one who has pointed out a real cause hitherto neglected in the calculations of geologists; and although we cannot accept the conclusions at which he arrives, we must acknowledge our admiration of this writer. His idea, in essence, may be briefly stated. Our globe in being carried round the sun, as modern astronomy teaches, has a path which is not a circle, but an ellipse. This, of itself, causes the earth to be nearer the sun in certain parts of its orbit, and farther away in others. But this elliptical path of the earth does not always maintain the same relation to the sun as a centre; it changes continually, and in the course of time, the aggregate of change is very considerable. At one time, the earth, at its nearest approach to the sun, is vastly nearer, and, at its farthest departure, vastly farther from that source of heat than it is at other times. The difference, as it is calculated by astronomers, is expressed in millions of miles. This element alone, however, would not give us any reason which could account for a change of temperature on the surface of the globe, because the motion of the earth being quickened in proportion to the nearness of its path to the sun, the amount of heat which it receives is the same when it is nearest as when

See the Reader for October 14th and December 2nd and 9th, 1864; also Philosophical Magazine, 1866, pp. 26, 27, 28, and 30.

it is farthest from the solar centre.

But there is another element which combines with what is called the eccentricity of the orbit. Winter and summer are not caused by our being farther from the sun in the one than in the other; but by that motion of the earth which shortens, or, as we may say of polar regions, blots out the winter's day, and lengthens the day of summer. In polar latitudes, the sun shines on the surface of the globe during the whole twenty-four hours of the summer's day, and is not seen at all in winter. It is on the effect of this, which arises from the turning away of the polar surface from the sun, that Mr. Croll chiefly depends for the proof of his theory. The radiations of heat must be excessive from the polar surface, when it is dark and at its greatest distance from the sun-when, too, because of its slow motion, its winter is at the longest. This loss of heat (as Mr. Croll argues) will not be compensated by the sun's nearness in summer; for the shortness of that season, from the swiftness of the earth's motion, in proportion to the length of the winter, will prevent all that would otherwise make the summer warm. Put, then, these two things together-let the northern winter occur when the earth is farthest from the sun, and, consequently, the summer when it is nearest-the winter will then be excessively severe, and the short summer, not even usually warm. This, Mr. Croll thinks, will cause a glacial period over great part of the northern hemisphere. Now, let the case be reversed-the short winter occurs when the earth is nearest the sun in space, and the long summer when it is farthest away. The consequence of this will be greatly lessened radiation in winter, and the equalizing, to a great extent, of that season and the summer in northern regions. These opposite combinations of the earth's position, in relation to the source of heat, account, according to this view, for regularly recurring periods of extreme winter cold, combined with proportionally small summer heat, such as will fail to melt the winter snow, and periods when the summer and winter are lost in constant spring. Could we confine our reasoning to astronomical theory, and leave out other considerations of a geographical nature, Mr. Croll would, we think, make out a pretty strong case by his argument for a "glacial period," during the time when the winter occurs at our greatest distance from the sun. But this is not the problem which is of greatest importance, as we are constrained to view the case, -that has respect to a hot climate sufficient for palms and turtles in our northern latitude. Mr. Croll does not attempt to make out this. He has difficulty in making out a period fit even for the ferns of the coal-measures, when winter occurs

at our nearest to the sun in the earth's eccentric orbit. He argues only for a "perpetual spring." His mean temperature, calculated for Great Britain, is only 60° F. This, he argues, must have been the summer and winter heat, with scarcely any variation, in the Carboniferous period. But, as we have seen, geology calls for the climate of the hottest parts of India, an equatorial climate whose mean heat is 81°. What we want is, at least, a tropical climate in the latitude of London-a climate very different indeed from that which, even according to revised ideas, could suit the vegetation of the Coal period. In thinking of the possibilities of such a climate in the North, it is necessary to keep in mind the truth to which we have already referred, that the length of the polar summer's day, though giving great advantage in the reception of heat by the constantly enlightened parts, presents only a slanting face to the sun, and so can never account for the heat and other effects which flow from the vertical radiance of Bengal. Sir Charles Lyell, in criticising Mr. Croll's theory, quotes from the Encyclopædia Britannica, the results of the reasoning there given in the article on climate. It is to the effect that the sun's rays passing through the atmosphere, so as to fall on the earth's surface at the equator, give 115° of heat, for 51° given in latitude 45° south or north, and for 14° given at either pole. The latitude of the London clay is 51° 30' N. The radiance of the sun, which gives 115° F. at the equator, and gives only 51° as far as 45° north latitude, is required to give an equatorial heat more than six degrees further north than where it can give only 51°. How will Mr. Croll, or any one else, make this out, and so explain on this theory the tropical remains in the isle of Sheppey? Yet this is that for which an account is required as the facts of geology stand.

The remains which, as we have seen, are imbedded in the London clay and kindred formations, are such that nothing short of the sun's vertical radiance will account for them. Dr. Hook saw this as early as 1688, and although his idea has been scouted, it is not on that account the less true. But, in addition to all this, any one who has had to do with the growth of palms and other tropical plants in this country, knows that it is not so much want of heat which renders it impossible to grow them satisfactorily, nor is it the want of moisture. These can be supplied; but what we lack is the sun's tropical radiance. Sunshine means much more than mere heat. How to show that this ever fell on the

*Lyell's Principles of Geology, vol. i., edition 1867, p. 284.