344 



SCIENCE. 



[N. S. Vol. XVII. No. 426. 



national eomplection to the scheme. To this 

 root is added a suffix which varies in a defi- 

 nite way so as to indicate class, order, rang 

 and grad. For these respective divisions, the 

 letters n, r, s, t are employed, in conjunction 

 with the vowel a, thus giving in English, ane, 

 are, ase and ate. In subclass, suborder, etc., 

 the vowel is changed to o, thus giving one, 

 ore, ose and ote. An example of the working 

 of the system may prove of interest. 



In many parts of the world in recent years 

 occurrences of a peculiar syenite have been 

 found, the rocks being rich in alkalis and 

 usually light in color. They sometimes con- 

 tain a little nepheline; in other cases this 

 mineral is absent. A number of names have 

 been given to local varieties of this rock, 

 pulaskite, nordmarkite, lauvikite, etc. When 

 any new occurrence is described an attempt 

 is made to bring it under one or other of 

 these terms, or perhaps a new varietal name 

 is suggested. How many of these varieties, 

 often more or less overlapping one another in 

 their characters may eventually be named, 

 it is at present difficult to say. 



Now, under the proposed system, the noi-m 

 of any new occurrence having been ascer- 

 tained, it would at once be seen that the rock 

 belonged to the class persalane, for the feld- 

 spars would form almost the entire rock. Then 

 it would be found that the quartz or nephe- 

 line present occurs in very small amount, less 

 than one seventh of the feldspar. This would 

 bring the rock into the fifth order of the 

 persalanes, namely, the canadares. The ques- 

 tion as to the proportion of the alkalis and 

 the lime in the rock would then present itself. 

 If this proportion be more than seven to one, 

 the rock belongs to the first rang of the cana- 

 dares and is a nordmarhase. If, further, the 

 soda is dominant over the potass, being pres- 

 ent in the proportion of between three fifths 

 and one seventh, the rock belongs to subrang 

 4 and is a nordmarhose. If the relative pro- 

 portion of lime to alkalis be greater than one 

 to seven, the , rock falls into rang 2 and is a 

 pulasTease — and, the relative proporton of soda 

 and potass remaining as above, into the sub- 

 rang lauvihose. 



It will thus be seen that it is possible to com- 



pare accurately the newly described vaj-iety 

 with those types already established and to 

 classify it with that with which it is most 

 nearly identical. The name assigned to it, 

 moreover, shows at once just how and to what 

 extent it differs in composition from any and 

 each of the varieties already known. 



As will be seen, the volcanic or plutonic 

 character of the rock (so important in the 

 schemes of classification employed by Rosen- 

 busch or Zirkel) has not been taken into con- 

 sideration in naming the rock. A qualifying 

 adjective, however, is prefixed to indicate the 

 texture of the. rock, which is, as a general 

 rule, determined by its solidification at the 

 surface or in the depths of the earth's crust. 

 The qualifying adjectives employed are those 

 now in general use, viz., granitic, trachytic, 

 ophitic, porphyritic, etc. This, added to the 

 magmatic name, will give a compound name 

 which accurately describes not only the com- 

 position, but the texture of the rock. 



It is impossible to refer to more than the 

 main outlines of this new scheme of classifi- 

 catibn, but, as will be found by perusal of the 

 book, the whole question has been most care- 

 fully thought out, every possible case consid- 

 ered and the scheme tested by applying it to 

 thousands of rock analyses. It, further, has 

 the merit of being presented in clear and idio- 

 matic English, so that it can be readily un- 

 derstood. It is the result of some ten years' 

 work on the part of four of the ablest petrog- 

 raphers in America, during which time many 

 different methods of classification have been 

 successively drawn up and tested, only to be 

 found to break down in some important par- 

 ticular. The present scheme is thus the re- 

 sult of a long course of investigation and 

 very mature deliberation. With a little ex- 

 perience the calculations required for the ap- 

 plication of the system can be quickly made, 

 especially with the aid of the tables given in 

 the book for that purpose. By such calcula- 

 tions, furthermore, it is possible to check the 

 accuracy of the chemical analysis of the rock 

 and in many cases to point out the natiu-e 

 of errors, if any have been made. A higher 

 degree of accuracy is thus secured in petro- 

 graphical investigation. 



