1882.1 273 [Chase. 



mined hj a summation ot all the tendencies to revolution which bear upon 

 each and all the molecules of the rotating body, and that tidal variations 

 of weight or pressure are as important in earth- and ocean-tides as in at- 

 mospheric tides. 



221. " There is much Virtue in ^." 



Pome extracts from a lecture by Dr. Ball, the Astronomer Royal of 

 Ireland, have lately been largely copied by the newspapers. They con- 

 tain a statement that the moon was once only 40,000 miles, away, and that 

 it thus acted as a geological engine of transcendent power. The state- 

 ment is somewhat qualified by the proviso that if the present tides are 

 three feet, and if the early tides were 216 times their present amount, then 

 it is plain that the ancient tides must have been 648 feet. This qualifica- 

 tion is not sufficient, and it is misleading, because it will be generally un- 

 derstood as covering all the points about which there is any uncertainty. 

 Science in its claims of exactness, cannot afford to hazard any claims 

 which can be easily refuted. It is true that there are many astronomers 

 who believe that Delaunay's views are correct, but there are probal;)ly few 

 who think that they have been conclusively demonstrated. If the moon 

 pulls the ocean-waters around the earth, in a direction opposite to its daily 

 rotation, at the rate of a thousand miles an hour, or at any less rate ; if 

 the friction, which would result from such a pull, is not compensated in 

 some way which is not yet fully known ; if there is a bulge of tidal water 

 which cannot fully keep up with the moon, and which, by its attraction 

 on the moon, tends to retard its orbital velocity; if all the mathematical 

 conclusions which it seems reasonable to draw from such supposed retard- 

 ation are correct, and if the "reproach" of thermodynamics must be ac- 

 cepted without qualification, the moon may be receding from the earth. 



•^ 222. Weakness of the Postulates. 



In examining the provisos of the foregoing note, we find : — In the first 

 place, no tidal currents have ever been observed which indicate a lagging 

 tendency in ocean waters. Secondly, there is no evidence whatever to 

 show that the earth's rotation has been retarded by friction. Thirdly, 

 there is no evidence to show that the moon's orbital motion has been re- 

 tarded by the ocean tides. Fourthly, the number of elements which must 

 enter into any calculation of planetary disturbances is so great that no 

 prudent mathematician ever looks for more than an approximation to 

 such results as he desires. Fifthly, the difficulties which are encountered 

 in trying to explain irregularities of orbital motion, are vastly enhanced 

 Avhen we come to deal with the complicated tendencies of planetary rota- 

 tion. Sixthly, there is as much reason to believe that the moon may be 

 gradually falling to the earth, as there is to believe that the earth may be 

 gradually falling to the sun. Seventhly, the accelerating and retarding 

 tendencies ot aethereal elasticity and resistance are but little understood. 

 Eighthly, all of the pos-sible compensatory adjustments, to which I have 



