INSTRUCTIONS. 



The present volume consists of three parts : — 



(a) Schedules and Indexes in four languages 



(b) An Authors' Catalogue. 



(c) A Subject Catalogue. 



The Subject Catalogue is divided into sections, each of which is 

 denoted by a four-figure number between OCOO and 9999. These 

 numbers follow one another in numerical order, but all the 9999 

 numbers are not used, for it is intended to fill up the gaps by interpola- 

 tion of such additional sections as may be required for additions to the 

 system of classification in futiu'e 3'ears, 



To enable the reader to find these numbers quickly, the first or last 

 number on the page is repeated at the head of the page. In looking 

 up a subject, these numbers, which are called Registration numbers, 

 should be used instead of the ordinary pagination. These Registration 

 numbers serve to divide up the subject into sections, each of which 

 deals with related matter. It has been sought, as far as possible, to 

 separate, for instance, spherical and dynamical astronomy methods, 

 calculations and observations ; and also to classify under Sun, Moon, 

 Planets, Comers, Double Stars, &c,, &c,, and in many cases to have 

 further sub-divisions for observations of a different character of the 

 same object, e.g., observations of position will, as a rule, be found 

 separated from spectroscopic or other physical observations, drawings, 

 &c. 



To save space, the separate planetar^^ headings are only given 

 under jMercur3% the third figure in the number being the same for 

 similar observations of any other planet; e.g., observations of 

 position of i^appho will be found under o9lU; markings on Mars 

 5«40, &c.. &c. 



