Abstract of Meteorological Observations in Brazil. 361 



thorough examination of the two acids which are contained 

 in the North American columbite: I very soon ascertained, 

 after the discovery of niobic acid, that this was the principal 

 acid constituent in the American columbite, but I could not 

 determine whether it was mixed with pelopic or with tantalic 

 acid; I therefore addressed myself to Mr. B. SilHman of New- 

 haven, who with the greatest readiness procured me a very 

 considerable quantity (half a pound) of this now very rare 

 mineral. 



A large quantity of this columbite was used for the prepara- 

 tion of the acid. When treated in the same manner as that 

 from the Bavarian columbite, it proved to consist principally 

 of niobic acid combined with pelopic acid; but the amount of 

 the latter was far smaller than in the Bodenmais mineral, so 

 that I do not think it would have been possible for me to have 

 examined the properties of pelopic acid so completely as was 

 necessary in order to recognise it as an essentially distinct acid 

 from tantalic acid, if I had had only the American mineral atmy 

 disposal. But both the acids were so perfectly identical in all 

 their properties with the two acids prepared from the Boden- 

 mais mineral, that I did not find the least diiference, even as 

 regards the specific gravity. 



As the specific gravity of pelopic acid is considerably higher 

 than that of niobic acid, when the two are heated in the same 

 manner, the higher specific gravity of the Bavarian columbite 

 is thus satisfactorily explained. 



I have moreover found small quantities of tungstic acid in 

 the acids from the American columbite, as well as in those 

 from the Bodenmais mineral. 



LVI. Abstract of Meteorological Observations made during the 

 year 1846 at Gongo Soco, i?i the interior of Brazil. By 

 William Joky Henwood, F.li.S., F.G.S., Member of the 

 Geological Societi/ of France, Chief Commissioner of the 

 Gold Mines of Gongo Soco, Catta Preta, and Antonio 

 Pereira, Src. 4c. * 



I HAVE nothing to add to vv])at has been already saidf 

 respecting the locality and the positions of the instru- 

 ments, I have again to thank Captains Blaney, Luke and 

 Guy, for the continuation of their midnight observations, as 

 well as for a second series, made at 3 a.m. 



* Communicated by the Author. 



t Phil. Mag. 184G,xxviii. pp. 364,360. 



