114 Scientific Intelligence. 



6. On the Products of Eruption at Hecla; by Dr. F. A. Genth of 

 Marbury. — The substances from Hecla examined by Dr. Genth were 

 received by him from Prof. Bunsen. The following are the results of 



some of his analyses. 



Lava of Tkjorsd. — This lava has a grayish black color and con- 

 tains chrysolite along with a new feldspathic mineral which Dr. Genth 

 calls Thjorsauite. The lava in its mixed state atForded — Silica 49*60, 

 aluminas 16*89, protoxyd of iron 11*92, trace of protoxyds of manga- 

 nese, cobalt and nickel, magnesia 7'56, lime 13*07, soda 124, potash 



20=100 48. 



The Thjorsauite afforded silica 48*36, alumina 30*59, peroxyd of 



iron 1*37, magnesia 097, protoxyd of manganese trace, lime 17*16, 



l ft * 



> « * 



soda M3, potash 0-62=100-20, giving the formula 2R 3 Si 2 -f 5A1SL 

 It is supposed to be monoclinate in crystallization like common feld- 

 spar, and has a distinct cleavage in one direction. Lustre vitreous, but 

 pearly on a cleavage face. Color white to grayish. Transparent. 

 Specific gravity at 17°, 2-688. Hardness=6. Before the blowpipe in 

 thin splinters it melts to a glass. Dissolves in borax. Insoluble in hy- 

 drochloric acid. In composition it is near scapolite whose formula is 



» * • ■ > . 



2R 3 Si 2 -f-4AlSi. The chrysolite of the lava has the specific grav- 



ity 3-226. 



)f Hals. — This lava has a grayish black color, with an 



imperfectly crystalline texture. Specific gravity at 5° C.:=2919. 

 H. =5-5-6. Slightly magnetic. Analysis gave silica 55*92, alumina 

 15*08, protoxyd of iron 15-18, protoxyd of manganese a trace, mag- 

 nesia 4*21, lime 6*54, soda 2*51, potash 095= 10039. Dr. Genth 



■ • • ■ . ■ i # * 



* deduces the approximate formula R 3 Si 2 -f- Al Si 2 . It is however a 

 rock consisting of two or more distinct minerals. 



Among the other rocks described in this memoir, the lava of 1845 

 afforded the same formula of composition as the preceding. 



The ashes of 1845 afforded silica 56*89, alumina 14*18, protoxyd 

 of iron 13-35, protoxyd of manganese 0*54, magnesia 4*05, lime 6*23, 

 soda 2-35, potash 2-64, which is nearly identical with the lava. 



7. On the Nummulite Limestone of Alabama ; by C. Lyell, (Proc 

 Geol. Soc, Jan. 9, 1847.*)— Mr. Lyell after statin* that the so-called 

 Nummulites Mantelli of Morion was distinguished by Prof. E. Forbes 

 and Lonsdale as a coral near Orbitolites instead of a "true Nummulites, 

 cites a note from D'Orbigny, in which this author observes that it is nca 

 Orbitolina but pertains to his new genus Orbitoides, and should there 

 fore be called Orbitoides Mantelli. 



r 



III. Zoology. 



1. .Some Notes on Mexican Birds, heretofore not fully described; 

 by George A. McCali,, U.S.A., (Proc. Acad. Nat. Set., Philad., May, 

 1848, p. 63.) — Orpheus curvirostrisj Swainson. — Length 10 inches, 



* See also this Journal, ii ser., vol. iv, p. 186. 

 t Called by Mexican peasants *< Ouitacoche. 



n 



