33^ ^f ^^^^ Propagation of Heat 



the Water at the Bottom of fresh Lakes ^ that are very 

 deep^ may be actually salt, 



AT the end of a French translation of the First 

 Edition of this Essay, published at Geneva, Pro- 

 fessor Pictet (the translator) has added the following ex- 

 tract of one of my private letters to him (of the 9th 

 of June, 1797), written in answer to one from him to 

 me, acknowledging the receipt of a manuscript copy of 

 the Essay which 1 had sent him. 



" I should have been much surprised if my Seventh 

 Essay had not interested you ; for in my life I never 

 felt pleasure equal to that I enjoyed in making the ex- 

 periments of which I have given an account in that 

 performance. You will perhaps be surprised when I 

 tell you, that I have suppressed a whole Chapter of 

 interesting speculation, merely with a view of leaving 

 to others a tempting field of curious investigation un- 

 touched^ and to give more effect to my concluding re- 

 flection, which I consider as being by far the most 

 important of any I have ever published." 



As these assertions (which were not originally in- 

 tended for the public eye) are liable to several inter- 

 pretations, I think it my duty, not only to explain them, 

 but also to let the Public know precisely how far I have 

 pushed my inquiries in the investigation of the subject 

 under consideration : This is an act of justice which I 

 owe to those who may be engaged in the same pursuits; 

 for it would be very unfair, by obscure hints of important 

 information kept back ^ to keep others in doubt with respect 

 to the originality of the discoveries they may make in 

 the prosecution of //zd-ir investigations. This would tend 

 to damp the spirit of inquiry, instead of exciting it ; and 



