33^ Of the 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 I 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 their investigations. This would tend 

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



