282 
Dr. Charles Hutton on 
names and nature of the several rocks that compose it, with 
tables or lists of their densities or specific gravities. In one 
table is a list of thirteen specimens of densities, contained 
between the numbers 2.6109 and 2.6656, the medium of the 
whole being 2.639876. In another table, of fifteen speci- 
mens, the densities are limited between 2.71845 and 3.0642, 
the medium of all which is 2.81039. And the mean between 
these two means, gives 2.725 for the medium density of the 
whole mountain, admitting it to be quite solid, or without 
vacuities, as it appears to be on the exterior surface at least. 
But in the calculation in my Tracts I went even a little higher, 
using the number 2.75 or 2J5 thus x 2^, which gives or 
4.95 for the mean density of the earth. Or, if we assume 
the density of the mountain still higher, as 2.8 instead of 
2.75, we then obtain -f- x 2.8 = 5.05, a little more than 5 for 
the earth's density ; which last number 5, 1 therefore fix upon, 
in conclusion, as probably the nearest to the truth ; or at 
least it is sufficiently large, as it is grounded on several as- 
sumptions that are most favourable for the highest result ; 
namely, 2.777714, or for the density of the mountain; 
also 1 as rather above the calculated ratio of the densities of 
O 
the earth and mountain ; and lastly, the assumption of the 
mountain being quite solid ; though it is probable that there 
may be cavities in most mountains, as they are generally the 
production either of volcanoes, or of earthquakes. 
For all these reasons, then, it is highly probable, that the 
earth's mean density is very near five times the density of 
water; but not higher. If any person should still hesitate 
to adopt this conclusion, his hesitation must arise from doubts 
either on the data obtained by the measurements, or on the 
