The Variation in Attraction Due to the Attracting Bodies. 251 



33. The interior density and tempprature of Mars. 



Newcomb says the mean density of Mars is 4.17 times water. Using 3.20 

 for the crust, the center density figures out 5.10. The compression for a 

 fifty-six miles crust, or about 11000 a'mospheres is .041, or .0000037 per 

 atmosphere. These results are claimed to be only rough approximations. 

 From them, nevertheless, it is doubtless safe to conclude that Mars is a 

 solid to the center, that his interior heat has nearly all escaped and that 

 the water and the air has been considerably absorbed in the interior of the 

 planet. 



34. The interior temperature of the eartli. 



The variation in the r'ensity of the tartli from surface to center is given 

 in Table 4. which has already been described. The conditions of this table 

 require that the temperature of ths interior layers ba tHe same, which 

 would be practically so in case of a moulten or liquid interior per law of 

 convec'ion. The compression for the one hundred and twenty -seven miles 

 crust, or about 600U0 atmosphere on the interior at temperature zero, 

 should be .0000037 multiplied by 60000, or .222. The compression for the 

 same crust of the earth in its presents condition given in Table 4 is only 

 .11, or computed to three decimal places is .114. The difference .108 is 

 caused by internal heat. This difference, .108 divided by .00003 gives the 

 interior temperature to be 3600° Centigrade. 



34. Interior density and temperature of Venus. 



Newcomb gives 4.81 for the mean density of Venus, and 7,660 miles for 

 her mean diameter or 258 miles less than the mean diameter of the earth, 

 On the hypothesis that Veuus has a moulten interior and a crust about 

 the thickness of that of the earth, by using 3 for the crust density we get 

 the required mass into the plaret with a center density of 7, and a crust 

 compression factor of .0913. T -le compression for one hundred and tsventy 

 three miles crust or aSout 49,000 atmospheres is at temperature zero .1813. 

 The difference between .1813 and .0913 divided by .00003 gives for the in- 

 terior temperature of Venus 3000' Centigrade. Per Newcomb the gravity 

 on the surface of Venus is .82, Mars .39, Earth 1 . 



35. The interior density and temperature of Mercury. 



Mercury has a meaa density, per Newcomb, 6.85, and a diameter of 

 about 3000 miles, and also a surface gnvity .46. The Moou's diam ter is 

 2160 miles, mean density 3.33. crust densi y 3.20 and center density 3.52. 

 Mars diameter is 4211 miles, mean density 3.17, sui'face density 3.20, center 

 density 5.10, and surface grivity .39. 



Without computation judging by a glance from the figures from the 

 Moon and Mars, the crust density of Mercury must be from 5 to 5.50. 

 Proctor thinks that 6.85 is too great for the mean density, and that it 

 should be about that of the earth, 5.65. Unrter this condition Mei-cury"s 

 crust density would be from 4 to 4.30. The smallnnss of the diameter of 

 this planet indicates that its interior heat has all or nearly all escaped. In 



