102 Selections from the Correspondence of 



that it may be of use in the improvement of knowledge in every 

 part of physics. I know not whether your taste be in this [de- 

 partment ?] of learning ; but whether or not, I must beg the fa- 

 vor of you to desire some of your mathematicians, those chiefly 

 versant in the Newtonian and Leibnitzian systems to peruse it, 

 (of which no doubt you have some of distinguished character in 

 your university.) and that you will favor me with your own and 

 their opinion of it, as soon as your conveniency permits. I ear- 

 nestly beg you to do it without compliment, and with the sin- 

 cerity and freedom of a friend and philosopher, as you see I 

 endeavor to write to you. 



This country is now engaged in a most barbarous war with 

 Indians, popish converts, set on by accursed priests to murder in- 

 nocent people in their beds, or at their daily labor. Good God, 

 what a religion must that be that incites men to such cruelties ! 

 And yet, from what we learn from the public news, your country 

 seems not sufficiently apprehensive of being again subjects of 

 such a bloody and cruel tyranny. 



The piece referred to in the foregoing letter was doubless his 

 " Explication of the first causes of actioti in matter, and of the 

 cause of Gravitation ;" which was first privately printed in New 

 York, and afterwards (in 1746) reprinted in London without the 

 author's knowledge. An enlarged edition, with the author's cor- 

 rections, was published in London in 1751, with the title, " The 

 principles of action in matter, the Gravitation of bodies, and the 

 motion of the planets explained from those principles ." An ex- 

 tract from the preface of this treatise, exhibiting an outline of 

 Mr. Colden's views, to which he attached high importance, is 

 given in Sparks, Works of Franklin, Vol. 6, p. 96. 



Dr. Colden to Gronovius. 



New York, Oct. 1st, 1755. 



To Dr. John Frederic Gronovius, Senateur de la ville de Leiden. 



It is so long since I had the favor of a line from you, that I 

 have frequently lamented the loss I sustain by being deprived 

 of that correspondence with which you once honored me. Soon 

 after my last to you, my time was so entirely taken up in the 

 public affairs while the last war continued with France, that I 



