26 



HENRY S. WASHINGTON 



olivine, the proportions of these being reversed. In the Monte Raneri 

 type, also, the amount of labradorite is somewhat less than in the 

 preceding rocks, while the ores and apatite remain about the 

 same. 



Chemical composition. — The results of an analysis made of the 

 freshest specimen from Monte Raneri are here given. As compared 



SiO^. . 



AUO3. 



Fe^Oa. 



FeO... 



MgO.. 



CaO. 



Na,0. 



K,0.. 



H2O + 



H2O- 



CO2... 



TiOj.. 



p,o,.. 



Cr^Oj. 

 MnO.. 

 NiO... 



100. 64 



Camptonose (olivine-basalt). Monte Raneri, Linosa. 



with those of the preceding types the siHca is decidedly lower than 

 the lavas of Monte Ponente, but only shghtly lower than the block 

 from II Fosso. Alumina, the oxides of iron, the alkahes, titanium, 

 phosphorus, and manganese are almost the same ; but lime is consider- 

 ably lower, and magnesia, on the other hand, very much higher, these 

 last features being in accord with the great abundance of olivine in 

 this type and its comparative paucity in augite. Nickel also seems to 

 be present in somewhat greater amount, and this is to be expected on 

 account of the high content in magnesia, though the small figures are 

 not very significant. Only a mere trace of chromium is present, and 

 none of this was detected in the other rocks analyzed. 



Occurrence. — Typical examples of this rock were found only at 

 Monte Raneri, where they seem to be the prevaihng type, but a very 

 similar lava was met with as blocks at Monte Rosso, in which, how- 

 ever, the oHvine phenocrysts, while prominent, are fewer and smaller 

 than in the Monte Raneri rock. 



