IV PREFACE 



spectrum series has been revised consistently with the now generally accepted 

 nomenclature. Certain standard values adopted for the International Critical 

 Tables, prepared under the auspices of the International Research Council, have 

 been inserted. These will be found included in the table on page 408. Some of 

 the added data has been inserted in the appendix to avoid renumbering the pages 

 of the body of the Tables for this reprint; it will be inserted in proper sequence 

 in the next edition. Gratitude is especially due to the members of the Bureau 

 of Standards, of the Nela Research Laboratory, to Dr. White of the Geophysical 

 Laboratory, Dr. Washburn of the National Research Council, and others for 

 data and suggestions. 



Frederick E. Fowle. 

 astrophysical observatory, 

 Smithsonian Institution, 

 February, 1923. 



