binations. 10

Division and arrangement in the natural sciences. 10

Difficulty of entitling a subclass corresponding to every
combination. 11

Expedients to reduce the number of subdivisions. 12

Superiority and inferiority. 15

Definite positional relationship of subdivisions. 16

Indented schedules. 17

Bifurcate division. 19

Utility of arrangement according to resemblances. 19

Definition. 20

Cross-references and search-notes. 21

Diagnosis to determine classification. 22

Claimed or unclaimed disclosure. 22

Diagnosis of pending applications. 23

Difficulties due to varying ideas of claims. 25

C. Rules of classification. 26

Basis of classification. 26

1. "Art" as the basis. 26

2. Operative or manipulative arts. 26

3. Structures. 26

4. Composition of matter and formed stock. 26

Division and arrangement. 27

5. Exhaustive division; miscellaneous subclass. 27

6. Subclasses not to overlap. 27

7. Subclasses of any group to be formed on one basis. 27

8. Apparent exception to rules 6 and 7. 27

9. Relative position of subclasses. 27

10. Indention of subclasses. 29

11. Different kinds of titles for subclasses. 29

12. Arrangement to limit search and cross references. 30

Definition. 30

13. Tentative definition. 30

14. How to define. 30

15. Explanatory notes may sometimes displace definitio