LETTER OF TRANSMITTAL. 



New York, July 24, 1894. 

 The Committee of the American Association for the Advancement of 

 Science having charge of Indexing Chemical Literature has voted to recom- 

 mend to the Smithsonian Institution for publication the three following 

 Indexes : — 



An Index to the Literature of Cerium. 

 An Index to the Literature of Lanthanum. 

 Both by W. H. Magee, Ph. D. 



An Index to the Literature of Didymium.'^ 

 By A. C. Langmuir, Ph. D. 

 The latter has already appeared in the School of Mines Quarterly, No. i, 

 Vol. XV. 



H. CARRINGTON BOLTON, 



Chairman. 



To the Secretary of the Smithsonian Institution. 



1 This Index is printed as Smithsonian Publication No. 972. 



