COMMON THINGS THE EARTH. 



same result, showing that the earth is a mass of matter about 5| 

 heavier than an equal volume of water, or, what is the same, that 

 the mean density of the earth is 5|, or, more exactly, 5*67 times 

 the density of water. 



Among the substances which have nearly the same density as 

 the earth may be mentioned, arsenic, chromium, chloride of silver, 

 oxides of copper and zinc, and peroxide of iron. 



40. The average weight of each cubic foot of the earth being 

 5-67 times the weight of a cubic foot of water, is 354-375 Ibs., or 

 0-1587 of a ton. It follows, therefore, that the total weight of 

 the earth is more than 6000,000000 billions of tons. 



