24 GEOLOGICAL MEMOIRS. 



By this easy experiment it appears that in some parts there was a 

 strong tendency to the formation of spheres, and which existed even 

 in the interior of the larger spheres, giving rise to smaller spherules. 

 M. Giimbel goes on to describe phenomena of a somewhat similar 

 nature which he has observed in melted and cooling metals, such as 

 lead and antimony ; and, as Leydolt noticed that some results of the 

 action of fluoric acid on glass * are explanatory of the structure of 

 agate, so has the author made similar observations when sheet lead 

 has been acted upon by the vapour of sulphuric acid. M. Giimbel 

 offers some remarks on the different sorts of agates, and notices that 

 the subject is in many respects of great interest, especially as regards 

 the formation of oolite, the spherical structure of basalt, &c. 



[T.R.J.] 



On Matlockite. By C. Rammelsberg. 



[Leonhard u. Bronn's N. Jahrb. f. Min. u. s. w. 1853, p. 173 : Poggend. Annal. 

 Ixxxv. p. 141 et seq.l 



The new mineral, Matlockite f, is very similar in external appearance 

 to Corneous Lead (Murio-carbonate of Lead, Blei-hornerz), and, to- 

 gether with the latter, it has been found, associated with earthy galena, 

 at the deserted Cromford mine, near Matlock. Both are very rare. 



Compact fragments of the Murio-carbonate are transparent, colour- 

 less or yellowish, lustrous, and pretty generally cleavable in three 

 directions at right angles to each other. Brooke :{: and Krug von 

 Nidda§ describe the crystals of this mineral. Rammelsberg found 

 its specific gravity to be 6*305. In powder it was in some degree 

 decomposed even by cold water, chlorite of lead being set free. Its 

 analysis is given below. 



In Matlockite, a single, but very perfect, plane of cleavage has 

 been observed. This mineral has been recognized as a basal chloride 

 of lead. The specific gravity of the powder is 5 •3947. Its analysis, 

 is — 



Matlockite. Blei-hornerz. 



Chlorine. ... 14- 12 1 rf. f.^ Carbonic acid. . . . 7*99 



Lead 41-50/ ^^'^'^- Oxide of lead. .. . 40-46 



Lead 41-50\.. ^o Chlorine 12-97 



Oxygen .... 2-88 / ^^''^^' Lead 37-96 



100-00 99-38 

 [T. R.J.] 



On GLAXJBERiTE/rom South Peru. By M. Ulex. 



[Leonhard u. Bronn's N. Jahrb. f. Min. u. s. w. 1851, p. 204 ; and Woehl. u. Lieb. 

 Ann. vol. Ixx. p. 51 et seq.'] 



The Brongniartin or Glauberite occurs in crystals imbedded in no- 

 dular masses of a substance called " Tizza," which the author recog- 



* See also Comptes Kendus, xxxi. p. 565. 



[t See also Lond. & Edinb. PhU. Mag. 4 ser. vol. ii. p. 120. — Tbansl.] 



t Poggendorf 's Annalen, xlii. p. 582. 



§ Zeitschrift d. Deutsch. geol. Gesellschaft, vol. ii. p. 126. 



