DENSITY OF THE EAETH. 17 



tenance of organic life. The size and figure of the ter- 

 restrial globe its mass (i. e. the quantity of matter of 

 which it consists, and which, compared with its volume, 

 determines its density, and thereby, under certain conditions, 

 . its internal constitution, as well as the measure of its 

 attracting force) ; are all connected with each other by an 

 interdependence, more distinctly recognisable and more 

 accessible to mathematical treatment than that which we 

 have as yet been able to perceive in the vital processes 

 above alluded to, in thermal currents, or in the telluric 

 conditions of electro -magnetism and chemical changes of 

 substances. Relations which, in complicated phsenomena, 

 we are not yet able to measure quantitatively, may yet exist, 

 and may be rendered probable on grounds of induction. 



Although we cannot, in the present state of our know- 

 ledge, reduce to the same law the two kinds of attraction 

 viz. that which acts at sensible distances (as the mutual 

 gravitation of the heavenly bodies), and that which acts at 

 distances immeasurably small (molecular or contact-attrac- 

 tion), yet it is not on that account the less credible, that 

 capillary attraction, and the action of endosmose, so im- 

 portant in the ascent of sap and other juices and for the 

 whole of vegetable and animal physiology, may be affected 

 by the amount and relations of gravity, as may also electro- 

 magnetic processes and chemical action. We may assume, 

 to take extreme circumstances, that if our planet had only 

 the mass of the Moon, so that the force of gravity at its 

 surface should have only about one-sixth of its present 

 intensity, the meteorological processes of our climates, the 

 hypsometrical relations of our mountain- chains, and the 

 physiognomy (facies) of our vegetation, would all be very 



VOL. IV. * 



