Geology and Mineralogy. 67 



He closes with the following paragraph : 



The large proportion of iron in the constitution of the earth 

 indicated by meteorites is in accord with the earth's density, 

 rigidity, and magnetic proportions. Assuming the density of 

 the rocks of the earth's crust to be 2*8, which may be too high, 

 and combining with it metal of the density of 7*8, which is an 

 average of the density of iron meteorites, it will be found that 

 77*58 per cent of metal will be required to obtain a density of 

 5*57, that of the earth as a whole. This is very nearly that of 

 the sum of the metals in the above result after eliminating the 

 proportions present as oxides. Such a proportion of iron would 

 seem to be in accord, as has been stated, with the earth's 

 rigidity and magnetic properties. 



8. The Mineralogy of Pennsylvania. Part Two. Chemical 

 Analyses ; John Eteeman. Pp. 25. Easton, Pa., 1911. — The 

 first part of these contributions was issued more than twenty 

 years ago, and was noticed in the Journal at that time (see vol. 

 xxxvii, 501, 1889). The present part contains chemical analyses 

 of many species, and also records of new localities. Unfortu- 

 nately the results of a large number of analyses made were 

 destroyed by fire sometime since, but those here given are numer- 

 ous and will be of value to mineralogists. 



9. Praktikum cler experimentellen Mineralogie • von Dr. 

 Ernst Sommerfeldt. Pp. xi, 192, 61 text figures, 1 plate. Ber- 

 lin, 1911 (Gebruder JBorntraeger). — This is a convenient little 

 book for the student who must instruct himself in practical min- 

 eralogy. It takes up briefly the successive parts of the subject, 

 and on the chemical side is much fuller than the elementary 

 textbooks usually are ; there is, for example, a chapter giving the 

 fundamental principles underlying the phenomena of fusion and 

 crystallization of substances under different conditions. 



10. Uraninite from German East Africa.— The uraninite 

 locality in the mica quarries of the Uruguru Mts., German East 

 Africa, has recently afforded, as announced by R. Brauns, a large 

 cubic crystal weighing 154 grams and measuring 3'5X 2*5x2 cen- 

 timeters. The specific gravity found was 7*7 ; that of the pure 

 nucleus being 8*84 and of the crust 4*82. The locality was first 

 described by W. Marckwald in 1906.— Centralblatt Min., 1906, 

 p. 761 ; 1911, p. 689. 



11. Production of Platinum in 1910. — The increased demand 

 for platinum in recent years, chiefly caused by its use in jewelry, 

 and the resulting rise in price reaching $45 per ounce in Septem- 

 ber, 1911, gives especial interest to the advanced chapter by W. 

 Lindgren on its production in 1910 from Mineral Resources of the 

 United States. Unfortunately the increased demand has thus far 

 brought no considerable increase in quantity. In this country 

 crude platinum is obtained in small quantities from the placer 

 mines of California and Oregon. The amount for 1910 was 337 

 and 53 ounces respectively. The production of crude platinum 

 in troy ounces for the world at large for 1909 and 1910 is given 

 in the following table. 



