82 Scientific Intelligence. 



subsequently consolidating there. The dikes are described as 

 streaky (schlierig) and as unusually rich in apatite, containing 

 as much as 8 per cent, fluidally arranged. These nuxional struc- 

 tures would appear to be the strongest evidence in support of the 

 igneous origin of the carbonate dikes. Further evidence is 

 afforded by the complete series of transitional rocks from pure 

 silicate rocks (ijolites) to pure carbonate rocks. Many of these 

 intermediate rocks have excellent "eutectic" structure, which is 

 regarded as sure proof of their igneous origin, but in view of the 

 fact that in recent years many of the so-called eutectic inter- 

 growths have been shown to be due to replacement, this criterion 

 has not the absolute value that the author attaches to it. 



From the petrographic resemblance of the central mass of 

 limestone of the Fen area to the sovite dikes, it also is interpreted 

 as of igneous origin. The possible length of the limestone area 

 is 2 km. and its width is 1 km. The intrusive carbonatites and 

 older rocks are cut by aliio'itic dikes, and all are intruded by 

 diabase dikes, but these last injections are not believed to have 

 any genetic relation with the Fen magma and its consanguineous 

 rocks. 



Daly's hypothesis for the origin of alkaline rocks is appre- 

 ciatively considered, but it is believed that at Fen the parent 

 magma was essexitic rather than basaltic. Igneous activity 

 began at Fen by the formation of a volcanic conduit by a gigantic 

 explosion. The essexite magma dissolved at great depth large 

 quantities of limestone, thereby producing the melteigite magma, 

 which, by gravity differentiation eventually yielded urtite. 

 After differentiation the carbonate magma swam on top of the 

 heavier silicate magma and finally solidified in the throat of the 

 volcano. Subsequently the volcano has been very deeply eroded, 

 and to this great denudation is ascribed the marked difference 

 between the igneous phenomena revealed at Fen and those in the 

 Christiania region : at Fen the phenomena are those due to deep- 

 seated igneous activity, whereas in the Christiania region they 

 are those produced in the comparatively shallow depths of the 

 earth's crust, adolph knopf. 



4. Mineral Resources of the Philippine Islands for 1919 and 

 1920. Pp. 70, with 4 plates and 4 text figures. Manila, 1922.— 

 The mineral production of the Philippines has increased from 

 234,000 pesos in 1907 to 7,611,000 pesos in 1920. In money value 

 gold is much the most important, namely 3,000,000 pesos (1916), 

 2,620,000 (1919), 2,425,000 (1920.) Coal increased from nearly 

 400,000 pesos (1918) to over 800,000 {1919) and 1,452,000 

 (1920). Salt, sulphur, stone and sand, with other products, are 

 also important. Iron ore exists though not yet developed and 

 the existence of a high grade of petroleum is believed to be 

 assured when active work of prospecting can go on. 



