INTRODUCTION 



'55(8) Geology of S. America. 



'55(85) Geology of Peru. 



[See Table C : Place divisions.] 



Divisions by Relation. A book may deal with two or 

 more subjects, or with a subject in its relation to some other 

 topic. After assigning to the book the number denoting its 

 first or principal subject, we may link on to this number, by 

 means of a colon, the number denoting the second or sub- 

 sidiary subject. Thus : 



6 1 1 : 612 Anatomy and Physiology. 



*6 1 1 : 7 Anatomy in its relation to Art. 



These different methods of division may be freely used in 

 combination. Thus : 



55(115 : 85)04 Essays on the coal strata of Peru. 



So long as only the ordinary digits are used in the class 

 numbers, the arrangement of books on the shelves presents 

 no difficulty. They follow each other in the ascending order 

 of the decimal fractions employed. Thus : 



'5 

 504 



'53 



5726 



61 



But when brackets and colons are used as well as digits, 

 it is convenient to adopt the convention that these come in 

 the alphabetical order of their names (bracket, colon, digit), 

 the cipher taking precedence of all three on the familiar 

 indexing principle, ''Nothing precedes something". Thus : 



5504 



55(85) 

 '55 : 59 

 '55 :7 

 '553 



