56 The American Geologist. January. 1905 
calculation of the norm this rock is found to be persalane, of order 
6, russare, damachalic viezzenase, and dosodic, viezzenose; which 
means that the salic minerals preponderate, that the feldspars are 
dominant over the feldspathoids, that the alkalies are dominant 
over lime and soda over potassa. 
2. Dioryte. The two principal areas are near San Jos6 and 
the rock is a typical dioryte. 
B.—Porphyritic Type. 
1. Andesyte. The laccolitic mass is exposed for twelve 
square miles in the centre of which is situated the town of San 
Jose. Two types are distinguished and an analysis of one is given 
and is shown to be a laurvikose in which the salic constituents and 
the feldspars preponderate; in which the alkalies are dominant 
over lime and soda over potassa. 
2. Dacyte. This is a more siliceous facies of the andesyte 
found in the hills south of San Jose of which two types are dis- 
tinquished. 
3. Basalt. It is a bluish black lava extending along the Ar- 
rayo Grande for four or five miles. 
C.—Dyke Rocks. 
The dyke rocks of the region about San Jos6 are separated into 
two groups striking at right angles to each other. Acid tinguaytes 
strike east and west and a basic series of camptonytes vogesytes 
and limburgytes strike north and south. The tinguaytes are 
divided into a porphyritic type and an aphanitic tinguayte bearing 
analcite. 
A discussion of the chemical relations of the San Jose rocks 
closes the paper. 
There is a wide range between the acid and the basic rocks 
but the tabulated analyses show a definite sequence the nature of 
which is indicated by the writer. 
The paper is illustrated by a geological map of the San Jos6 
district, by ten photomicrographs of the igneous types and five 
views of the mountains surrounding San Jos6. A. J. 
The Geology of the Cerrillos Hills, Xew Mexico. By Douglas Wil- 
son Johnson. (Contributions from the Greological Department 
of Columbia University, vol. x, No. 90.) 
This paper is a discussion of the igneous hills in the region of 
Cerrillos, New Mexico, with a detailed description of the surround- 
ing sedimentary formations. The subject is treated in three parts: 
Part I. is concerned with the stratigraphy, physiography, geologic 
history and economic products of the district; Part II. contains a 
description of the palaeontology of the sedimentary formations; 
Part III. gives an account of the petrogrraphy of the igneous for- 
mations. 
