VI TABLE OF CONTENTS. 



ART. PAGE 



to the cosine of the angle which its direction makes with the normal to 

 the surface. Divers remarks, and considerations on the object and extent 

 of thermological problems, and on the relations of general analysis with 

 the study of nature 22 



SECTION II. 



GENERAL NOTIONS AND PRELIMINARY DEFINITIONS. 



22 24. Permanent temperature, thermometer. The temperature denoted 

 by is that of melting ice. The temperature of water boiling in a 

 given vessel under a given pressure is denoted by 1 26 



25. The unit which serves to measure quantities of heat, is the heat 

 required to liquify a certain mass of ice . . . . . . .27 



26. Specific capacity for heat ib. 



27 29. Temperatures measured by increments of volume or by the addi 

 tional quantities of heat. Those cases only are here considered, in which 



the increments of volume are proportional to the increments of the 

 quantity of heat. This condition does not in general exist in liquids ; 

 it is sensibly true for solid bodies whose temperatures differ very much 

 from those which cause the change of state 28 



30. Notion of external conducibility ib. 



31. We may at first regard the quantity of heat lost as proportional to the 

 temperature. This proposition is not sensibly true except for certain 

 limits of temperature . . . . . . . . .29 



32 35. The heat lost into the medium consists of several parts. The effect 



is compound and variable. Luminous heat ib. 



36. Measure of the external conducibility . . . . . . . . 31 



37. Notion of the conducibility proper. This property also may be observed 



in liquids ^ 



38. 39. Equilibrium of temperatures. The effect is independent of contact . 32 

 40 49. First notions of radiant heat, and of the equilibrium which is 



established in spaces void of air ; of the cause of the reflection of rays 

 of heat, or of their retention in bodies ; of the mode of communication 

 between the internal molecules; of the law which regulates the inten 

 sity of the rays emitted. The law is not disturbed by the reflection of 



heat . ibt 



50, 51. First notion of the effects of reflected heat 37 



52 56. Remarks on the statical or dynamical properties of heat. It is the 

 principle of elasticity. The elastic force of aeriform fluids exactly indi 

 cates their temperatures ....... 39 



SECTION III. 

 PRINCIPLE OF THE COMMUNICATION OF HEAT. 



57 59. When two molecules of the same solid are extremely near and at 

 unequal temperatures, the most heated molecule communicates to that 

 which is less heated a quantity of heat exactly expressed by the product 

 of the duration of the instant, of the extremely small difference of the 

 temperatures, and of a certain function of the distance of the molecules . 41 



