"trate one another, but powers, such as we

know do in fact exift in the fame place, "and counterbalance or over-rule one an"other; a circumftance which never had the appearance of a contradiction, or even of a difficulty.

"If the momentum of fuch a body in mo"tion be fufficiently great, Mr. Bofcovich "demonftrates that the particles of any body, "through which it paffes, will not even be "moved out of their place by it. With a degree of velocity fomething less than this

(6

they will be confiderably agitated, and ig-. "nition might perhaps be the confequence, "though the progrefs of the body in motion "would not be fenfibly interrupted; and "with a ftill lefs momentum it might not "pafs at all." Theoria Philofophiæ Naturalis, p. 167.

"This theory Mr. Bofcovich has taken a great deal of pains to draw out at full "length and illuftrate; fhewing that it is by "no means inconfiftent with any thing that "we know concerning the laws of mecha"nics, or our difcoveries in natural philofophy, and that a great variety of phenomena, particularly those which relate to light, "admit of a much easier folution upon this hypothefis than upon any other.

"The most obvious difficulty, and indeed "the only one that attends this hypothefis, as it fuppofes the mutual penetrability of "matter, arifes from the difficulty we meet "" with

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"with in attempting to force two bodies into "the fame place. But it is demonftrable, that "the firft obftruction arifes from no actual "contact of matter, but from mere powers of

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repulfion. This difficulty we can overcome; and having got within one fphere "of repulfion, we fancy that we are now impeded by the folid matter itself. But the very fame is the apprehenfion of the ge"nerality of mankind with refpect to the first "obstruction. Why, therefore, may not the

next resistance be only another sphere of "repulfion, which may only require a greater force than we can apply to overcome it, without disordering the arrangement of the "conftituent particles; but which may be overcome by a body moving with the amazing velocity of light.

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"This fcheme of the mutual penetration of matter, firft occurred to Mr. Michell on reading Baxter on the Immateriality of the "Soul. He found that this author's idea of "matter was, that it confifted, as it were, " of bricks cemented together by an imma"terial mortar. Thefe bricks, if he would "be confiftent in his own reasoning, were

again compofed of lefs bricks, cemented "likewife by an immaterial mortar, and fo "on ad infinitum. This putting Mr. Michell upon the confideration of the appearances "of nature, he began to perceive that the "bricks were fo covered with this immaterial mortar, that, if they had any existence at

C 3

“all,

all, it could not poffibly be perceived, every "effect being produced at least in nine in"ftances in ten certainly, and probably in "the tenth alfo, by this immaterial, fpirit"tual, and penetrable mortar.

"Inftead, therefore, of placing the world 66 upon the giant, the giant upon the tor"toise, and the tortoife upon he could not "tell what, he placed the world at once up"on itself; and finding it ftill neceffary, in "order to folve the appearances of nature, to "admit of extended and penetrable imma"terial substance, if he maintained the im

penetrability of matter; and observing farther, that all we perceive by contact, &c. "is this penetrable immaterial fubftance, and

not the impenetrable one; he began to "think that he might as well admit of pene"trable material, as penetrable immaterial "fubftance; efpecially as we know nothing "more of the nature of fubftance than that "it is fomething which fupports properties; "which properties may be whatever we pleafe, provided they be not inconfiftent "with each other, that is, do not imply the "abfence of each other.

r

"This by no means feemed to be the case "in fuppofing two fubftances to be in the "fame place, at the fame time, without ex

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cluding each other, the objection to which "is only derived from the resistance we meet "with to the touch, and is a prejudice that "has taken its rife from that circumftance,

" and

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"and is not unlike the prejudice against the antipodes, derived from the conftant ex"perience of bodies falling as we account it "downwards.

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"I hope I fhall be excufed dwelling fo

long on this hypothefis, on account both "of the novelty and importance of it, efpecially with refpect to the phenomena of "light. If I were to make any alteration in "it, it would be to fuppofe the force of the sphere of repulfion next to any of the in

66

divifible points, which conftitute what we "call folid bodies, not to be abfolutely infi"nite, but fuch as may be overcome by the "momentum of light; which will obviate "the objection of Mr. Melville. If, how66 ever, we confider that Mr. Bofcovich "makes this nearest power of repulfion not "to extend to any real space, but to be con"fined to the indivifible point itfelf, it may

appear to be fufficient for the purpofe; "fince the chance of fuch points impinging upon one another is fo little, that it needs "not to be confidered at all."

Of the Seat of the SENTIENT PRINCIPLE in Man.

N the two preceding fections I have endea

IN

voured to rectify the notions which we have been taught to entertain concerning matter, as not being that impenetrable, inert fubftance that we had imagined it to be. This, being admitted, will greatly facilitate our farther progrefs in thefe difquifitions; as I hope we shall not confider matter with that contempt and difguft, with which it has generally been treated; there being nothing in its real nature that can juflify fuch fentiments respecting it.

I now proceed to inquire whether, when the nature of matter is rightly understood, there be any reafon to think that there is in man any fubftance effentially different from it, that is, any thing poffeffed of other properties befides fuch as may he fuperadded to thofe of attraction and repulfion, which we have found to belong to matter, or that may be confiftent with thofe properties. For if this be the cafe, true philofophy, which will not authorize us to multiply caufes, or kinds of fubftance, without neceffity, will forbid us to admit of any fuch fubftance. fuch fubftance. If one kind of fubftance be capable of fupporting all the

known