358 Mr. W. J. M. Rankine on the Reconcentration of 



It thus appears, that by means of observations of the excess 

 of the mean temperature of rivers above those of the atmosphere 

 and of the soil, we may test the soundness of the supposition 

 that that excess is wholly or partly produced by friction ; and if 

 that supposition be found to agree with the facts, we may calcu- 

 late, from observations on diflferent streams under different cir- 

 cumstances, the numerical values of the constants C and C. 



In order that the observations may be capable of yielding 

 satisfactory residts, they should be made upon a variety of streams 

 of different forms of section, inclinations and velocities ; and the 

 part of each stream at which the temperatures are observed 

 should have a form of section, an inclination, and a velocity, as 

 nearly as possible uniform. 



The following quantities should be observed : — 



1 . The inclination of the stream, i. 



2. Its area of section, s. 



3. The breadth of itfj surface, b. 



4. The periphery of its bed, p. 



5. The velocity of the current, v. 



6. The mean temperature of the air. 



7. The mean temperature of the soil of the bed. 



8. The mean temperature of the stream. 



The observations of temperature were made by M. Renou 

 every day at the hours of 4 a.m., 6 a.m., and every hour till 

 10 P.M. inclusive. 



The effect of the solar heat can easily be tested, either by 

 observing the temperature of a piece of stagnant water adjoining 

 a river, of equal depth and similar form and constitution of bed 

 (for the temperature of such a ])iece of water would exhibit the 

 effect of the solar radiation unaffected by that of friction), or by 

 continuing the observations of the temperatures of the river 

 and of the atmosphere during the night. 



As I do not yet know the form, dimensions, inclination, or 

 velocity of the Loir, I am for the present unable to illustrate the 

 principles stated above by numerical examples. 



LVI. On the Reconcentration of the Mechanical Energy of the 

 Universe. By William John Macquorn Rankine, C.E., 

 F.R.S.E. c^c* 



'IIE following remarks have been suggested by a paper by 

 Professor William Thomson of Glasgow, on the tendency 

 which exists in nature to the dissipation or indefinite diffusion 

 of mechanical energy originally collected in stores of power. 



* Communicated by the Author ; having been read to the British Asso- 

 ciation for tlie Advancement of Science, Section A, at Belfast, on the 2nd 

 of September 1852. 



