At present we are accustomed to admit action at sensible distances, as of one magnet upon another, or of the sun upon the earth, as if such admission were itself a perfect answer to any enquiry into the nature of the physical means which cause distant bodies to affect each other; and the man who hesitates to admit the sufficiency of the answer, or of the assumption on which it rests, and asks for a more satisfactory account, runs some risk of appearing ridiculous or ignorant before the world of science. Yet Newton, who did more than any other man in demonstrating the law of action of distant bodies, including amongst such the sun and Saturn, which are nine hundred millions of miles apart, did not leave the subject without recording his well-considered judgment, that the mere attraction of distant portions of matter was not a sufficient or satisfactory thought for a philosopher. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is, he says, to him a great absurdity. Gravity must be caused by an agent, acting constantly according to certain laws; but whether this agent be material or immaterial he leaves to the consideration of his readers. This is the onward looking thought of one, who by his knowledge and like quality of mind, saw in the diamond an unctuous substance coagulated, when as yet it was known but as a transparent stone, and foretold the presence of a combustible substance in water a century before water was decomposed or hydrogen discovered: and I cannot help believing that the time is near at hand, when his thought regarding gravity will produce fruit: and, with that impression, I shall venture a few considerations upon what appears to me the insufficiency of the usually accepted notions of gravity, and of those forces generally, which are supposed to act at a distance, having respect to the modern and philosophic view of the conservation and indestructibility of force.

sun.

The notion of the gravitating force is, with those who admit Newton's law, but go with him no further, that matter attracts matter with a strength which is inversely as the square of the distance. Consider, then, as a mass of matter (or a particle), for which present purpose the sun will serve, and consider a globe like one of the planets, as our earth, either created or taken from distant space and placed near the sun as our earth is;-the attraction of gravity is then exerted, and we say that the sun attracts the earth, and, also, that the earth attracts the But if the sun attracts the earth, that force of attraction must either arise because of the presence of the earth near the sun; or it must have pre-existed in the sun when the earth was not there. If we consider the first case, I think it will be exceeding difficult to conceive that the sudden presence of an earth, ninety-five millions of miles from the sun, and having no previous physical connection with it, nor any physical connection caused by the mere circumstance of juxtaposition, should be able to raise up in the sun a power having no previous exist. ence. As respects gravity, the earth must be considered as inert, previously, as the sun; and can have no more inducing or affecting power over the sun than the sun over it: both are assumed to be without power in the beginning of the case ;-how then can that power arise

by their mere approximation or co-existence? That a body without force should raise up force in a body at a distance from it, is too hard to imagine; but it is harder still, if that can be possible, to accept the idea when we consider that it includes the creation of force. Force may be opposed by force, may be diverted, directed partially or exclusively, may even be converted, as far as we understand the matter, disappearing in one form to reappear in another; but it cannot be created or annihilated, or truly suspended, i. e., rendered existent without action or without its equivalent action. The conservation of power is now a thought deeply impressed upon the minds of philosophic men; and I think that, as a body, they admit that the creation or annihilation of force is equally impossible with the creation or annihilation of matter. But if we conceive the sun existing alone in space, exerting no force of gravitation exterior to it; and then conceive another sphere in space having like conditions, and that the two are brought towards each other; if we assume, that by their mutual presence each causes the other to act, this is to assume not merely a creation of power but a double creation, for both are supposed to rise from a previously inert to a powerful state.. On their dissociation they, by the assumption, pass into the powerless state again, and this would be equivalent to the annihilation of force. It will be easily understood, that the case of the sun or the earth, or of any one of two or more acting bodies, is reciprocal; and also that the variation of attraction, with any degrees of approach or separation of the bodies, involves the same result of creation or annihilation of power, as the creation or annihilation (which latter is only the total removal) of either of the acting bodies would do.

Such, I think, must be the character of the conclusion, if it be supposed that the attraction of the sun upon the earth arises because of the presence of the earth, and the attraction of the earth upon the sun, because of the presence of the sun there remains the case of the power, or the efficient source of the power, having pre-existed in the sun (or the earth) before the earth (or the sun) was in presence. In the latter view it appears to me that, consistently with the conservation of force, one of three sub-cases must occur: either the gravitating force of the sun, when directed upon the earth, must be removed in an equivalent degree from some other bodies, and when taken off from the earth (by the disappearance of the latter) be disposed of on some other bodies; or else it must take up some new form of power when it ceases to be gravitation, and consume some other form of power when it is developed as gravitation;-or else it must be always existing around the sun through infinite space. The first sub-case is not imag. ined by the usual hypothesis of gravitation, and will hardly be supposed probable for, if it were true, it is scarcely possible that the effects should not have been observed by astronomers, when considering the motions of the plants in different positions with respect to each other and the sun. Moreover, gravitation is not assumed to be a dual power, and in them only as yet have such removals been observed by experi ment or conceived by the mind. The second sub-case, or that of a new or another form of power, is also one which has never been imag. ined by others, in association with the theory of gravity. I made some

endeavors, experimentally, to connect gravity with electricity, having this very object in view (Phil. Trans. 1851, p. 1); but the results were entirely negative. The view, if held for a moment, would imply that not merely the sun, but all matter, whatever its state, would have extra powers set up in it, if removed in any degree from gravitation; that the particles of a comet at its perihelion would have changed in character, by the conversion of some portion of their molecular force into the increased amount of gravitating force which they would then exert ; and that at its aphelion, this extra gravitating force would have been converted back into some other kind of molecular force, having either the former or a new character: the conversion either way being to a perfectly equivalent degree. One could not even conceive of the dif fusion of a cloud of dust, or its concentration into a stone, without supposing something of the same kind to occur; and I suppose that nobody will accept the idea as possible. The third sub-case remains, namely, that the power is always existing around the sun and through infinite space, whether secondary bodies be there to be acted upon by gravitation or not: and not only around the sun, but around every particle of matter which has existence. The case of a constant necessary condition to action in space, when as respects the sun the earth is not in place, and of a certain gravitating action as the result of that previous condition when the earth is in place, I can conceive, consistently, as I think, with the conservation of force: and I think the case is that which Newton looked at in gravity; is, in philosophical respects, the same as that admitted by all in regard to light, heat, and radiant phenomena; and (in a sense even more general and extensive) is that now driven upon our attention in an especially forcible and instructive manner, by the phenomena of electricity and magnetism, because of their dependence on dual forms of power.

II. GEOLOGY.

1. Description of the Fossils and Shells collected in California; by WM. P. BLAKE, Geologist of the U. S. Pacific Railroad Survey in California, under the command of Lieut. R. S. Williamson, in 1853-54. 34 pp. 8vo. War Department, Washington, 1855.-The explorations of the Rocky Mountains and Western America by the Pacific Railroad Expeditions have brought in large contributions to science in its various departments, and it is most gratifying to know that they are to be published with full details and figures. The important pamphlet here referred to gives in brief some of the geological results in anticipation of the final Report. The facts are of special interest to the science, and we cite the general conclusions.

Report of Mr T. A. Conrad on the Fossil Shells collected in California by Wm. P. Blake.-I have examined the very interesting organic remains which you collected in California, and the drawings of such species as were too fragile to preserve, and I herein submit a few remarks upon their geological relations. There appear to be several distinct groups; but I cannot pretend, from such scanty materials, to designate what particular formation every group represents. There is no obscurity resting on the deposits of Santa Barbara and San Pedro,

which represent a recent formation, in which you inform me the remains of the mammoth occur. The shells are generally those which live in the adjacent waters, and indicate little if any change of temperature since their deposition. The littoral character of this formation is very evident. Water-worn shells and fragments show the action of the surf, whilst entire specimens of bivalves, and Pholadidæ, and Saxicavæ, remaining undisturbed in their self-excavated domicils, exhibit the same disposition of marine shells that is familiar to the observer on all sandy and argillaceous shores. They burrow in clay, mud or sand, beyond the ordinary action of the surf; whilst some are scooped out by the tempest-driven surge, and others preyed upon by fishes and marine animals of various kinds, and are thus broken up and deposited among the living species.

Of the Eocene, and the recent formation alluded to, I can speak with confidence; but the intermediate beds are of uncertain age. The Ostrea vespertina, Anomia subcostata and Pecten vespertinus, occurring in the bank of Carizzo creek, are unlike any recent forms that I am acquainted with from the Pacific coast, but analogous to Miocene species of Virginia. This formation may, therefore, be regarded as of Miocene origin-an opinion in which I am confirmed by some fossils collected in California, by Dr. Heermann, consisting of decidedly Miocene forms; a Mercenaria, (M. perlaminosa,) Con., scarcely differing from a species of Cumberland county, N. J., (M. Ducatelii, Con.), a Cemoria, Pandora and Cardita of extinct species, closely analogous to Miocene forms. I am inclined, also, to refer to this period a very dif ferent group from Ocoya creek, the forms of which you sketched in California, as the specimens were too friable to be preserved. I do not recognize any recent species among them, nor any contained in an Eocene deposit.

The rock at San Diego is replete with shells, generally of a small size, and appears to have a certain palæontological relation to those of Monterey, Carmello, and those from the rocks near Astoria in Oregon, collected by Townsend, and Dana, which I have referred to the Miocene period. Two species of San Diego, if not identical, approach Oregon shells; Nucula decisa is similar to N. divaricata, and both, in their markings, resemble N. Cobboldii of the English Miocene. Mactra Diegoana is nearly related to the Oregon M. alboria.

The Eocene period is unequivocally represented by the beautifully perfect shells from the Cañada de las Uvas, which, though not found in situ, are evidently derived from strata occurring on the Pacific slope of the Sierra Nevada. This is very remarkable, inasmuch as three species correspond with forms of Claiborne, Alabama, and seem to indicate a connexion with the Atlantic and Pacific oceans during the Eocene period. The vast distance between the two localities will account for the general distinction of species, and it was, indeed, an unexpected result to find any identical. If I had imagined any eastern species to occur in California, it would have been the very one which does occur, and, apparently, in abundance, that "finger-post" of the Eocene, Cardita planicosta, a fossil of the Paris basin, and also abundant in Maryland, Virginia, and Alabama. This species originated and perished in the Eocene period, and is so widely distributed that it may

be regarded as the most characteristic fossil of its era. As the boulder from which these shells were derived was quite small, and yet furnished thirteen species, when it shall be investigated in situ, doubtless a great many other forms will be obtained, and very likely some with which we are already familiar in eastern localities. Although the rock is a very hard sandstone, the shells may be exposed in great perfection by careful management, and we look forward with great interest to their further development, and to the discovery of the rock in situ.

List of Species.-[Species not new are marked with an asterisk; all are Conrad's except Natica gibbosa and Anodonta Californiensis of Lea, Cardita planicosta, and Fissurella crenulata of Sowerby.]

(1.) EOCENE.-Cardium linteum, Dosinia alta, Meretrix Uvasana, M. Californiana, Crassatella Uvasana, C. alta, Mytilus humerus, Cardita planicosta, Natica cetites, N. gibbosa, Turritella Uvasana, Volutatithes Calforniana, Busycon? Blakei, Clavatula Californica.

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(2.) MIOCENE AND RECENT FORMATIONS.-Cardium modestum, Nucula decisa, Corbula Diegoana, San Diego; Meretrix uniomeris, Monterey county; M. decisa, Ocoya creek; M. Tularana, Tulare valley; Tellina Diegoana, San Diego; T. congesta, Monterey, Carmello, and San Diego; T. Pedroana, San Pedro; Arca microdonta, Tulare valley?; Tapes diversum,* Saxicava abrupta, Petricola Pedroana, Schizothorus Nutalli, San Pedro; Lutraria Traskei, Carmello; Mactra Diegoana, San Diego; Modiola contracta, Monterey county; Mytilus Pedroanus, San Pedro ; Pecten Deserti, Anomia subcostata, Ostrea vespertina, O. Heermanni, Colorado desert; Penitella spelæum, San Pedro, (recent); Fissurella crenulata, San Pedro; Crepidula princeps, Santa Barbara; Natica Diegoana, Trochita Diegoana, San Diego; Crucibulum spinosum, ———— ? ; Nassa interstriata, N. Pedroana, Strephona Pedroana, Littorina Pedroana, San Pedro; Stramonita petrosa, Tulare valley; Gratelupia mactropsis, Meretrix Dariena, Tellina Dariena, Isthmus of Darien; Natica Ocoyana, N. geniculata, Bulla jugularis, Pleurotoma transmontana, P. Ocoyana, Scytopus Ocoyanus, Turritella Ocoyana, Colus arctatus, Tellina Ocoyana, Pecten Nevadanus, P. catilliformis, Cardium -? Arca Solen? Dosinia ? Venus ? Cytherea decisa? Ocoya or Posé creek; Ostrea -? Pecten ? Turritella biseriata, San Fernando; Trochus ? Turritella -?, Benicia; Buccinum interstriatum ? Olivia Pedroensis, San Pedro; Anodonta Californiensis, Colorado desert.

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Remarks in conclusion, by W. P. Blake.-From this report by Mr. Conrad, we find that in the collection of sixty-one determinable species, fifty-five are new and are now described for the first time. Of these, ten are from one locality at the southern extremity of the Tulare valley, at the entrance to the pass called the Cañada de las Uvas. They are considered to be of the age of the Eocene by Mr. Conrad, who notes the similarity between three of the species and those of the Alabama Eocene deposits at Claiborne. These fossils were imbedded in a boulder of compact sandstone that had been washed out of the ravine of the pass by floods. The rock was not found in situ at that point, but a few miles to the westward a similar rock occurs in place, and is replete with fossils. These are believed to be the first fossils of the Eocene age that have been procured from the Pacific slope of the United States.