16 SCIENCE PROGRESS 



I. Volcanic and Hypabyssal Alkaline Rocks 



i. Phonolite, Sokoto Hill, Mozambique. 



2. Phonolite, Sanhuti River, Mozambique. 



3. Solvsbergite, Sanhuti River, Mozambique. 



4. Phonolite, Athi Plains, British E. Africa. 



5. Phonolite, Black Hills, Wyoming, U.S.A. 



6. Phonolite, Montreal, Canada. 



7. Phonolite, Bohemia. 



8. Phonolite, Wolf Rock, Cornwall. 



9. Phonolite, Fernando Nironha Is., Brazil. 



10. Leucitophyre, Reiden, Eifel. 



11. Paisanite, Ailsa Craig, Firth of Clyde. 



12. Tinguaite, Serra de Tingua, Brazil. 



13. Solvsbergite, Gran, Hadeland, Sweden. 



Average radium content of 13 rocks = 2*94 x io~ 12 grams per gram. 



II. Plutonic Alkaline Rocks 



1. Foyaite, Serra de Monchique, Portugal. 



2. Ditroite, Ditro, Transylvania, Hungary. 



3. Laurdalite, Laurdal, Norway. 



4. Laurvikite, Laurvik, Norway. 



5. Miaskite, Miask, Urals, Siberia. 



6. Pulaskite, Fourche Mts., Arkansas, U.S.A. 



7. Leucite Syenite, Serra de Caldus, Brazil. 



8. Elaeolite Syenite, Serra de Tingua, Brazil. 



9. Nepheline Syenite, Renfrew Co., Ontario, Canada. 



10. Elaeolite Syenite, Langesund Fjord, Norway. 



11. Elaeolite Syenite, Magnet Cove, Arkansas, U.S.A. 



Average radium content of 11 rocks = 1*87 x io -12 grams per gram. 



III. Plutonic Ultrabasic Rocks 



1. Serpentine, Shetland Is. 



2. Serpentine, Ballantrae, N.B. 



3. Hornblende Peridotite, Portsoy, Banff. 



4. Enstalite Peridotite, Assynt, Sutherland. 



5. Serpentine, Knockdhu, Ayrshire. 



6. Serpentine, Rhode Is., U.S.A. 



7. Dunite, Lake Superior, Canada. 



8. Dunite, Dun Mt., New Zealand. 



9. Kimberlite, Transvaal. 



10. Peridotite, East Griqualand. 



Average radium content of 10 rocks =0-51 x io -13 grams per gram. 



As yet the data are rather too scanty to justify more than 

 a few wide generalisations. Strutt's results indicated that on 

 the average the acid rocks were richer in radium than those 

 of more basic composition. Later determinations did not at first 

 altogether support this view, chiefly because of the remarkably 



