$2 Scientific Intelligence. 



13,700 feet. The volcano is greatly eroded and is one of the 

 oldest of the group. Its age cannot be exactly told, but the tuffs 

 and ashes of the group cover sediments of Upper Cretaceous age 

 and contain plant remains representing the present flora. 



The chief interest lies in the igneous rocks which form the 

 lavas of the mountain. They are of highly alkaline types, and 

 among them are represented leucitite with phenocrysts of nephe- 

 lite, hauynite and augite, occasional pyrite and perofskite in a 

 groundmass of leucite, nephelite and augite, with some apatite 



Si0 2 Al a 8 Fe 2 3 FeO MnO MgO CaO Na a O K 2 H 2 P 2 5 Ti0 2 S0 3 CI C0 2 



1 [46-48 19-00 414 2-30 tr. 2"49 4-35 846 678 3-31 "15 1--22 '19 -08 -36= 99-91 



2 40-10 15-27 1013 1-85 -08 4 59 12-08 478 3*34 293 "87 3*64 — — "23= 99'89 



3 39-97 1730 7*41 305 '09 3*82 10-53 5-14 3 56 411 -84 3'34 --06 -14 -33= 99"89 

 439-30 13-66 7"42 4-45 -08 4"46 11-37 5'78 1*44 4-53 -85 3"62 2.17 -48 -15= 99-76 



5 39-37 16-50 2-28 7"97 -06 448 10 22 4-73 338 4"77 -13 331 2*14 -09 -64=10007 



6 38-39 12-64 7"40 615 '02 6'46 14-17 4-35 2"44 1-62 116 444 -47 '37 -23 = 100-31 

 7|40'15 I7'32 7-25 4-00 -08 4'43 11-78 5-99 3.78 1*18 *7l 321 — — -15 = 100-38 



1, Leucitite; 2, Leucite nephelinite ; 3, Leucite nephelinite, including ZrO 2 = -20; 

 4, Hauj^uophyre ; 5, Hauynophyre; 6, Nepheliuite. of a special variety ; 7, Normal 

 nephelinite, including Zr0 2 = *35. All analyzed by Dr. Max Dittrich. 



and perofskite. Leucite composes- about one-half the rock. Leu- 

 cite nephelinite also occurs, composed of augite, apatite and ores 

 in a groundmass of augite, leucite and nephelite, the latter pre- 

 dominating. Hauynophyres occur containing phenocrysts of 

 hauynite, augite and ore grains in a groundmass much like those 

 just mentioned. A nephelinite of a special variety in which the 

 nephelite in the groundmass is not fully individualized is also 

 described. Phenocrysts of augite,. hauynite, apatite and titanite 

 lie in a clear colorless base with microlites of augites and ore 

 grains. The colorless base is held to be partly individualized 

 nephelite. Nephelinites of normal type are also described and 

 the twinning and optical properties of the larger individuals is 

 made a special study. The accompanying table of analyses will 

 be of interest to petrographers. l. v. p. 



8. Sondre ITelgeland af J. H. L. Vogt. (Norges G-eologiske 

 Undersogelse No. 29, 1900, Kristiania, 8°, 180 pp., I map, 21 figs.) 

 — This work is devoted to an account of the geology of Helge- 

 land, the southern part of the district of Nordland in northern 

 Norway. With the exception of a small area of Archean the 

 region is composed of metamorphic schists and limestones, prob- 

 ably of Cambrian-Silurian age. The author divides the metamor- 

 phosed sediments into mica schist, marble, and a later gneiss. In 

 addition there are extensive areas of eruptive rocks consisting 

 mainly of soda granite and gabbro. Sometimes these are strongly 

 stretched and squeezed and are then held to have been injected 

 previous to the final dynamic foldings which gave birth to the 

 mountain chains; sometimes they are in normal condition and are 

 then held to be of contemporaneous or later age. 



