128 M. Melloni on (he Theory of Dew. 



a small scale, the effects of diluvian currents. Yet we know, 

 that the most feeble rivulet shews us in miniature all the 

 phenomena of a large river ; and everywhere in nature we see 

 the same effects produced on every kind of scale. Our oppo- 

 nents confess that a torrent never traces rectilinear striae ; 

 and yet they prefer to attribute them to torrents, rather than 

 admit that they were engraved by glaciers, which are every 

 day forming similar ones under our own eyes. 



These are the impossibilities which have prevented M. Du- 

 rocher drawing any conclusion from the facts he mentions in 

 his two memoirs. He endeavours to prove that these facts 

 ought not to be attributed to the action of a glacier ; but he 

 forgets to shew us how they can be explained with marvel- 

 lous facility on the hypothesis of one or many currents. This 

 however, he must do before he produce conviction in others. 

 But the author has so completely lost view of the conditions 

 of the hypothesis he has undertaken to dfjfend, that his ob- 

 jections to glaciers apply almost always with still greater 

 force to the supposition of one or more currents. 



I have not adverted to many of these objections, from the 

 fear of extending this refutation too far, and prolonging a dis- 

 cussion, which I leave in the hands of all geologists who have 

 seen existing glaciers, and compared their effects with those 

 observed in the plains of Switzerland and Scand/mavia. 



On the Theory of Derv. By M. Melloni ; in Two Letters 

 to M. Arago.* 



The violent attacks lately made on the theory of Wells, have 

 induced me again to take up the study of dew. After a very 

 long series of observations and experiments, often inter- 

 rupted and resumed, I think that I have arrived at a distinct 

 solution of all the questions connected with this interesting 

 phenomenon. The memoir in which they are described has 

 been read to our Academy of Sciences (at Naples) who have 

 been so attentive as to occupy themselves with the subject 



* Comptes Rendus des Seances de 1' Academic des Sciences, No. xiii., p. 531. 



