SOME UNSOLVED SCIENTIFIC PROBLEMS 



day. Yet Professor Darwin himself urges that there 

 are elements of fallibility in the data involved that rob 

 the computation of all certainty. Much the same thing 

 is true of perhaps all the estimates that have been made 

 as to the earth's ultimate fate. Thus it has been sug- 

 gested that, even should the sun's heat not forsake us, 

 our day will become month-long, and then year-long; 

 that all the water of the globe must ultimately filter 

 into its depths, and all the air fly off into space, leaving 

 our earth as dry and as devoid of atmosphere as the 

 moon ; and, finally, that ether-friction, if it exist, or, in 

 default of that, meteoric friction, must ultimately 

 bring the earth back to the sun. But in all these prog- 

 nostications there are possible compensating factors 

 that vitiate the estimates and leave the exact results in 

 doubt. The last word of the cosmic science of our 

 generation is a prophecy of evil if annihilation be an 

 evil. But it is left for the science of another genera- 

 tion to point out more clearly the exact terms in which 

 the prophecy is most likely to be fulfilled. 



PHYSICAL PROBLEMS 



In regard to all these cosmic and telluric problems, 

 it will be seen, there is always the same appeal to one 

 central rule of action the law of gravitation. When 

 we turn from macrocosm to microcosm it would appear 

 as if new forces of interaction were introduced in the 

 powers of cohesion and of chemical action of molecules 

 and atoms. But Lord Kelvin has argued that it is pos- 

 sible to form such a conception of the forms and space 

 relations of the ultimate particles of matter that their 

 mutual attractions may be explained by invoking that 



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