IV PREFACE. 



of tables, such as those here given, involving so much transcribing, interpolation, 

 and calculation, can be free from errors, but it is hoped that these are not so 

 numerous as to seriously detract from the use of the book. 



I wish to acknowledge much active assistance and many valuable suggestions 

 during the preparation of the book from Professors S. P. Langley, Carl Barus, 

 F. W. Clarke, C. L. Mees, W. A. Noyes, and Mr. R. E. Huthsteiner. I am also 

 under obligations to Professors Landolt and Bornstein, who kindly placed an 

 early copy of their " Physikalisch-Chemische Tabellen " at my disposal. 



Thomas Gray. 



Rose Polytechnic Institute, 



Terre Haute, Ind., July 13, 1896. 



