CONTENTS 



Original Papers 



Page 

 Physics. — Recent improvements in the petrographic microscope. F. E. 



Wright 465 



Physics. — The calculation of Planck's constant C 2 . J. H. Dellinger 472 



Physics. — Some new designs of radiometers. W. W. Coblentz 473 



Physics. — Criteria for gray radiation. P. G. Nutting 476 



Physics. — Summary of experiments on the silver voltameter at the Bureau 



of Standards. E. B. Rosa and G. W. Vinal 478 



Chemistry. — A note on the sulphone-phthaleins as indicators for the colori- 

 metric determination of hydrogen-ion concentration. Herbert A. Lubs 



and William Mansfield Clark 481 



Chemistry. — The colorimetric determination of the hydrogen-ion concentra- 

 tion of bacteriological culture media. William Mansfield Clark and 



Herbert A. Lubs 483 



Botany. — The early European history and the botanical name of the Tree 

 of Heaven, Ailanthus altissima. Walter T. Swingle 490 



Abstracts 



Physics 499 



Metrology 500 



Electro-Chemistry 500 



Paleontology 501 



Geology 502 



Technology 506 



References 



Terrestrial Magnetism 508 



Physics 508 



Physical Chemistry 513 



Geology s 514 



Entomology 515 



Engineering 515 



Proceedings 



The Washington Academy of Sciences 516 



The Geological Society 516 



The Biological Society 519 



