On the Mean Temperature of Rivers and the Atmosphere. 355 



the bricks, which is generally composed of sulphur, arsenic, an- 

 timony, iron and copper ; but in the fusing-fumace the bricks 

 are often consumed and worn quite thin. The destruction of 

 the bricks is greatest when fluxes are used ; and if these contain 

 chlorides, soda or potash, the corrosion of tlie building extends 

 a good way along the stack or culvert. Where copper is exposed 

 in the furnace, the oxides burning off often combine Math the 

 bricks and fuse into a solid cake. These deposits and sublima- 

 tions, their composition, and their causes, will be noticed in their 

 proper place. 



[To be continued.] 



L^''. On the Causes of the Excess of the Mean Temperature of 

 Rivers above that of the Atmosphere, recently observed bij 

 M. Renou. Bij William John Macquorn Ranking, C.E., 

 F.R.S.E. ^c* 



IT appears from the Comptes Rendus for the 14th of June 1852, 

 (vol. xxxiv. p. 916), that M. Renou of Vendome has for 

 four years made a series of daily observations on the temperature 

 of the river Loir at that place, as compared with that of the 

 atmosphere, and has found that the mean temperature of the 

 river invariably exceeds that of the air. 



His observations for 1851, being the only series yet published, 

 show that this excess varied between 1-^ and 3 Centigrade degrees, 

 and that its average amomit was 2°'24 Centigrade ; the mean 

 temperature of the river for the whole year having been 12°-08 

 Cent., while that of the air was 9°'8'i. 



A similar result has been deduced from a smaller number of 

 observations made on the Loire at Tours by IM. Oscar Valin. 



Those facts are interesting, not only in a purely meteorological 

 point of view, but also as aifording an illustration of an important 

 principle in the theory of heat ; and considering the ease with 

 which observations similar to those of M. Renou may be made 

 at any place where a meteorological register is kept in the neigh- 

 bourhood of a river, they appear to be well worthy of the atten- 

 tion of those members of the British Association who make 

 meteorology their study. 



The object of this paper is to point out how o1)scrvations on 

 the excess of the mean temperature of rivers above that of the 

 atmosphere may be made available for the advancement of our 

 knowledge of the theory of heat. 



As an argument favourable to the opinion suggested by 



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

 ciation for the Advancemcut of Science, Section A, on tlie 2nd of Sep- 

 tember 1B52. 



2 A2 



