1855.] On Mental Education. 463 



to associate gravity with them ; and perhaps enable us to know 

 whether the essential force of gravitation (and other attractions) 

 is internal or external as respects the attracted bodies *. 



Returning once more to the definition of the gravitating 

 power as " a simple attractive force exerted between any two or 

 all the particles or masses of matter at every sensible distance, 

 but ivith a STRENGTH VARYING inversely as the square of the 

 distance" I ought perhaps to suppose there ave many who 

 accept this as a true and sufficient description of the force, and 

 who therefore, in relation to it, deny the principle of conserva- 

 tion. If both are accepted and are thought to be consistent 

 with each other, it cannot be difficult to add words which shall 

 make " varying strength " and " conservation " agree together. 

 It cannot be said that the definition merely applies to the effects 

 of gravitation as far as we know them. So understood, it 

 would form no barrier to progress ; for, that particles at dif- 

 ferent distances are urged towards each other with a power 

 varying inversely as the square of the distance, is a truth ; but 

 the definition has not that meaning ; and what I object to is the 

 pretence of knowledge which the definition sets up, when it 

 assumes to describe, not the partial effects of the force, but 

 the nature of the force as a whole. 



June, 1858. M. F. 



Observations on Mental Education f. 



? [These observations were delivered as a lecture before His Royal Highness 

 The Prince Consort and the Members of the Royal Institution on the 6th of 

 May, 1854. They are so immediately connected in their nature and origin 

 with my own experimental life, considered either as cause or consequence, that 

 I have thought the close of this volume not an unfit place for their reproduction.] 

 I TAKE courage, Sir, from your presence here this day, to 

 speak boldly that which is upon my mind. I feared that it 



* Dr. Winslow, of West Newton (Mass.), U.S., states, that from the 

 examination of a record of 850 earthquakes and volcanic eruptions, it appears 

 that the greater number occur in the winter months, when the sun is nearest 

 to the earth, and the attraction of gravity greatest. Their occurrence is more 

 rare as the distance is greater, the number being for December 102, which 

 in the intervening months gradually decreases to and increases from 44 for 

 June. Hence he draws conclusions regarding other exhibitions of the gravi- 

 tating force than mere attraction, when that attraction is varied by change of 

 distance. Annual of Scientific Discovery. 



t Lectures on Education, 1855. Parker and Son. 



