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poreal substance, and* for a satisfactory account of the 

 manner of our own sensations. Yet without the true 

 notion of a body, we cannot understand the object of 

 physics in general: and without knowing the nature of 

 the sensation, we are ignorant of that, from which we 

 derive almost ail that we know of any body in parti- 

 cular. 



" And as our philosophical knowledge is not very 

 deep, not reaching with any certainty to the bottom of 

 the most obvious things, nor penetrating to their inmost 

 nature : so it is not very wide, not being able to give us 

 with any clearness or particularity, an account either of 

 the celestial parts of the world, or of the deeply subter- 

 raneous parts of which the superficial part is but a small, 

 not to say contemptible portion. As 'to the very globe 

 \ve inhabit, (not to mention how many plants and mi- 

 nerals we are wholly ignorant of, and Aiovv many others 

 we are but slenderly acquainted with) the objects about, 

 which our enquiries angl experiments are conversant all 

 belong to the superficial parts of the globe, of which the 

 earth known U us is but the crust. But what the iuter- 

 cal part of it is, we no more know, than what is the sub- 

 stance of the remotest stars. Even among the moderns 

 some think the internal part of it, is pure elementary 

 earth ! Others imagine it to be fire, the receptacle of 

 natural, or hellish flames. Others will have the earth to be 

 a solid magnet ; while others br-lieve it at once was fixed 

 star: and that though it is now degenerated into a planet, 

 yet its internal parts are of the same nature us before : 

 the cliange proceeding only from thick spots that cover it, 

 (like those frequently observed upon the sun) by the 

 condensation whereof the firm earth, whic!> we inhabit, 

 was formed. And it is as difficult to demonstrate the 

 fcils hood, as the truth, of each of these jarring opinion?. 

 For whereas it is at least three thousand five hund red 

 miles to the centre of the earth, it does not appear, that 

 men have been able to penetrate towards it either by 

 land, or by sea, above one, or two miles at the most, and 

 that not in above three or four places. So that as yet \ve 

 have not penetrated any thing deep upon the husk, with- 

 Ji 3, 



