369 



111 this sclieme the logical di vision of subjects has been sacrificed as 

 far as sociued lu-ccssaiy to increase the practical usefulness of the 

 index. The arrangement is such that new divisions and subdivisions 

 may be introduced without interfering with those previously made. 



One of the greatest difficulties in the classification of the subjects 

 treated in agricultural science arises from their mixed nature, due not 

 only to their economic relations, but also to their involving matters 

 which in a strictly scientific classification would belong under two or 

 more separate heads. This difliculty is increased by the practical 

 necessity of keeping the index within reasonable limitations as regards 

 size. As far as possible the duplication of entries by cross-references 

 is to be avoided in an index of this magnitude. As the work of the 

 ■ stations reaches out in many directions into the domain of pure as dis- 

 tinguished from applied science, it was deemed desirable to set apart 

 a ])ortion of the index for entries relating to the general principles of 

 the various sciences Avhich lie at the foundation of experimental inves- 

 tigations in agriculture. A further reason for this arrangement is that 

 there will thus be a place in the index where any works on science 

 which are found to be useful to students in agTicultural Lines can be 

 referred to. This will afford the widest opportunity for the extension 

 of the index by individual students for their own special purposes. It 

 should be clearly recognized that any attempted classification of such 

 varied and complex subjects will be more or less unsatisfactory to the 

 individual student. Experience will doubtless show in what direction 

 the classification adopted can be extended or improved. 



The index is printed on cards. This system has been adopted because 

 experience seems to show that it affords the greatest opportunity for 

 diversification of arrangement and for the indefinite extension of an 

 index under a single classification. The cards are of the standard library 

 size, individuals who have had most experience in the preparation and 

 use of card indexes being almost unanimous in advocating this size of 

 card. The divisions and subdivisions have been arranged on a deci- 

 mal system, and are plainly indicated by the use of division cards of 

 different colors. 



Each index card wiU contain the title of an article, the name of its 

 author, a reference to the publication in which it appeared and to the 

 ExiDeriment Station Record, and a condensed statement of its contents. 

 At the upper right-hand corner of the card is a number indicating 

 under A\^at head the card should be placed in the index. The order in 

 which the cards are printed is indicated at the lower left hand corner. 

 A key to the index, containing the system of classification, was sent 

 out with the first installment of cards. 



One copy of the index will be sent to each of the agricultural colleges 

 and experiment stations in the United States, where it will doubtless 

 be accessible to students of agricultural science who may desire to con- 

 sult it. 



