Revieivs — Prof. R. A. Daly — Igneous Rocks. 473 



composition, and consequently should belong to Harker's Calcic 

 or Pacific Branch of Igneous rocks, whereas the solvsbergites, 

 trachytes, etc., of Macedon, the phonolites of Omeo and Mansfield, 

 the essexites (?) of Caraperdown and Kyneton, and the tracliytes and 

 anorthoelase basalts of the Coleraine area must be placed in the 

 Alkali or Atlantic Branch. It follows, then, that the evidence of the 

 Victorian Kainozoic rocks does not support Harker's generalization 

 on Petrographic Kegions. 



A number of first-class analyses have been made of the principal 

 types of the Macedon Series, and variation diagrams based on these 

 analyses have been drawn (see Bulletin of the Geological Survey of 

 Victoria, No. 24, 1912, and Proceedings of the Royal Society of 

 Victoria, n.s., vol. xxvi, pt. ii, 1914). It was found that by 

 re-calculating the analyses to 100 per cent with the water omitted 

 and the ferric oxide reduced to ferrous, the curves obtained were 

 better than those plotted from the original analyses. Certain of the 

 analyses did not conform to the curves, and at first these were 

 regarded as representing hybrid types, but additional work showed 

 that they represented complementary types and resulted from the 

 splitting up of a magma instead of the mixing of magmas. A few 

 analyses have been made of the alkali rocks from other Victorian 

 areas, but a siifficient number have not been made to show the 

 relationship of the various types to one another. 



The conclusions are that the Kainozoic alkali rocks of Victoria are 

 derived from the calcic basalts by differentiation, giving rise to several 

 lesser magma reservoirs. In the case of the Macedon magma further 

 differentiation took place, and a series of lavas were extruded which 

 in general showed a serial relationship to one another, but a certain 

 number were complementary to one another. 



I^E^VIEAATS. 



I. — Igneous Rocks and their Origin. By R. A. Daly, Sturgis- 

 Hooper Professor of Geology, Harvard University. New York 

 and London, 1914. 



EVERY field-student of igneous intrusions must at some period of 

 I his career have been confronted by the following problem : 

 before the intrusion occurred, what occupied the space now filled 

 with igneous rock, and what has become of that material ? Up to the 

 present time this problem has scarcely been considered by British 

 petrographers, at any rate in print, whatever may have been their 

 private speculations" on the subject. This is the most important 

 question that the author of this book sets out to answer ; if, after 

 reading it, we are not perhaps prepared to accept all his conclusions 

 in full in exactly the sense intended by the author, it is at any rate 

 clear that he has provided abundant food for thought among 

 petrologists. 



Professor Dalv has long been known as an advocate of stopmg as an 

 important mechanism in rock-intrusion. Now, stoping is merely 

 another name for assimilation, since it implies the fusion and 



