H. 8. Washington — Rhyolites of Lipari. 



449 



while the third generally sinks slowly, its density as a 

 whole being slightly above 1. No section was made of 

 these pumices, but they seem to show no spherulites and 

 no phenocrysts. The refractive index of the pumice glass 

 was found, by Dr. Merwin, to be 1.499. 



Chemical composition. — Analyses were made of three 

 specimens : one a typical, black obsidian, free from gray 

 streaks and spherulites, from Eocene Rosse ; another of 

 a black obsidian with gray streaks and showing the yel- 

 lowish spherulites, from Forgia Vecchia; and one of a 

 " first quality" pumice, taken from the bins at Canneto, 

 but presumably from Monte Pelato. These analyses are 

 given in Table I, along with older analyses by Abich 

 and Grlaser of the same rocks. It is interesting to observe 

 how closely those made by Abich, published in 1841, cor- 

 respond with the most recent ones. They are, as in other 

 cases that I have noted, a striking testimony to his skill 

 as an analyst. 



TABLE I. 



12 3 4 5 6 



SiO, 74.22 73.86 71.70 74.05 74.37 73.70* 



A1 2 3 12.98 12.49 12.60 12.97 12.65 12.27 



Fe 2 3 0.40 0.60 0.48 2.73 2.58 2.31 



FeO 1.60 1.40 1.17 n.d. n.d. n.d. 



MgO 0.04 0.11 0.12 0.28 0.20 29 



CaO 0.67 0.75 0.79 0.12 1.22 65 



Na 2 4.13 4.05 4.15 4.15 3.87 4.52 



K 2 4.97 4.81 5.17 5.11 4.57 4 73 



H 2 0+ 0.27 0.92 3.15) 0.22) 



!■ 0.22 (. 1.22 



H 2 0— 0.04 0.09 0.20) 02 f 



Ti0 2 0.11 0.12 0.11 n.d. n.d. n d 



Zr ° 2 0.05 0.06 n.d. n.d. n.d. n!d! 



P2O5 0.14 trace trace n.d. n.d. n d 



S°« 0-08 0.06 n.d. n.d. n.d. n!d! 



CI • 0.03 0.26 0.14 0.31 n.d. 0.31 



£ n ® °- 01 trace trace none n.d. none 



EaU none none n.d. n.d. n.d. n.d. 



99.74 99.58 99.78 100.00 99.70 100.00 



Sp.gr 2.370 2.363 2.370 2.377 



1— Obsidian, Rocche Rosse, Lipari. Washington analyst. 



2.— Obsidian, Forgia Vecchia, Lipari. Washington analyst. 



3.— Pumice, Monte Pelato, Lipari. Washington analyst. 



4.— Obsidian, Rocche Rosse, Lipari. Abich analyst. Abich, Vulkan. Ersch., 



1841, Taf. Ill, p. 62; cf. p. 84. ' 



5.— Obsidian, Forgia Vecchia, Lipari. Glaser analyst. Bergeat, Abh. Bay 



Akad. Wiss., 20, 111, 1899. J ' 



6.— Pumice, Rocche Rosse, Lipari, Abich analyst. Abich, op. eit., p. 62, 



