Mineral Acids on Copper. 23S 



when the metal has been previously polished, that it has occur- 

 red to me, that thus coloured ruby-red, it might be useful in 

 the ornamental arts. 



To conclude. The phenomena noticed in the foregoing expe- 

 riments (so like what we see in the mineral kingdom), in which, 

 in the same specimen, we often witness the mixture of native 

 copper and its protoxide, and some combination with an acid, 

 offer an analogy not destitute of interest, and which may serve 

 to explain circumstances which have hitherto been enveloped 

 in mystery, as, the manner in which these minerals originated, 

 thus grouped together, and, I was about to add, the manner in 

 which they are preserved, retaining their lustre almost equally 

 unimpaired in the recesses of the metallic vein, and in the cabi- 

 net of the mineralogist ; but this latter peculiarity has already 

 been explained most satisfactorily, by the electro-chemical re- 

 searches of Sir Humphry Davy. 



Corfu, April IT. 1827. 



On the Mean Temperature of the Atmosphere and of the Earthy 

 in some parts of East Russia. By Professor A. T. Kupffer. 

 With a Plate of Isogeothermal Lines. 



A HE thermometrical observations, which form the basis of the 

 following determinations, were made with rectified thermome- 

 ters. I first determined with care the error of a mercurial ther- 

 mometer of Pixii, in Paris, which I intended to use as a normal 

 thermometer. I did this according to the method described by 

 Bessel, in these Annals, b. 82, p. 287, a very necessary precau- 

 tion ; for, although the boiling and freezing points were pretty 

 accurately fixed, yet the error of the instrument, one way or 

 another, amounted to a whole degree. With this normal ther- 

 mometer, the others were now carefully compared, and their in- 

 dications corrected by a table formed for the purpose. 



Temperature of the Air in Kasan. 



This was daily observed in the shade, for a whole year, at 

 9 A. M., 12 noon, 3 and 9 r. m., in an apartment selected for 



4 



