VOL. LXV.] PHILOSOPHICAL TRANSACTIONS. J IQ 



traction being inversely as the square of the distances, comes out about double 

 this. Whence it should follow, that the density of the hill is about half the 

 mean density of the earth. But this point cannot be properly settled till the 

 figure and dimensions of the hill have been calculated from the survey, and 

 thence the attraction of the hill, found from the calculation of several separate 

 parts of it, into which it is to be divided, which will be a work of much time 

 and labour ; the result of which, will be communicated at some future 

 opportunity. 



Having thus come to a happy end of this experiment, we may now consider 

 several consequences flowing from it, tending to illustrate some important ques- 

 tions in natural philosophy. 1. It appears from this experiment, that themoun» 

 tain Schehallien exerts a sensible attraction ; therefore, from the rules of phi- 

 losophizing, we are to conclude, that every mountain, and indeed every particle 

 of the earth, is endued with the same property, in proportion to its quantity of 

 matter. r ■ ij, 



2. The law of the variation of this force, in the inverse ratio of the squares 

 of the distances, as laid down by Sir Isaac Newton, is also confirmed by this ex- 

 periment. For, if the force of attraction of the hill had been only to that of 

 the earth, as the matter in the hill to that of the earth, and had not been greatly 

 increased by the near approach to its centre, its attraction must have been 

 wholly insensible. But now, by only supposing the mean density of the earth 

 to be double to that of the hill, which seems very probable from other considec4 

 ations, the attraction of the hill will be reconciled to the general law of the 

 variation of attraction in the inverse duplicate ratio of the distances, as deduced 

 by Sir Isaac Newton from the comparison of the motion of the heavenly bodies 

 with the force of gravity at the surface of the earth ; and the analogy of nature 

 will be preserved. ,; 



3. We may now therefore be allowed to admit this law ; and to acknowledge, 

 that the mean density of the earth is at least double of that at the surface, and 

 consequently, that the density of the internal parts of the earth is much greater 

 than near the surface. Hence also, the whole quantity of matter in the earth 

 will be at least as great again as if it had been all composed of matter of the 

 same density with that at the surface ; or will be about 4 or 5 limes as great as if 

 it were all composed of water. The idea thus afforded us, from this experiment, 

 of the great density of the internal parts of the earth, is totally contrary to the 

 hypothesis of some naturalists, who suppose the earth to be only a great hollow 

 shell of matter ; supporting itself from the property of an arch, with an immense 

 vacuity in the midst of it. But were that the case, the attraction of mountains, 

 and even smaller inequalities in the earth's surface, would be very great, contrary 

 to experiment, and would affect the measures of the degrees of the meridian 



