Septembeb 2, 1921] 



SCIENCE 



193 



in favor of establishing a four year course in 

 medicine at the university. The board will 

 prepare a bill for presentation at the nest 

 session of the legislature in 1923 to authorize 

 and appropriate money for the establishment 

 of a state hospital at Columbia to be operated 

 in conjunction with the medical school. 



Dr. H. J. Webber has been appointed profes- 

 sor of eitriculture in the University of Califor- 

 nia and director of the Citrus Experiment 

 Station at Eiverside, the position he held be- 

 fore he accepted an industrial position at 

 Hartsville, South Carolina. 



Professor A. V. Miller, associate profes- 

 sor of drawing and descriptive geometry, has 

 been apppointed assistant dean of the college 

 of engineering of the University of Wiscon- 

 sin, to take the place of Professor J. D. Phil- 

 lips, who is now acting business manager 

 during the year's leave of absence of H. J. 

 Thorkelson. 



. Dr. John Sundwall, professor of hygiene 

 and public health at the University of Minne- 

 sota, has been made director of hygiene and 

 public health in the newly established depart- 

 ment of physical education. 



In the Medical School, Boston, Dr. Fred 

 Wilbur Thyng has been promoted to be pro- 

 fessor of anatomy, and Dr. Jesse Leroy Conel 

 has been appointed assistant professor. 



Professor H. C. Plummer has been ap- 

 pointed professor of mathematics at the Ord- 

 nance College, Woolwich, England. 



DISCUSSION AND CORRESPONDENCE 



AN IMPORTANT BUT UNNAMED RADIOACTIVE 

 QUANTITY 



The problems that are met in the quanti- 

 tative study of radioactive materials and proc- 

 esses fall naturally into two classes. One class 

 includes the strictly chemical problems; the 

 other, the problems that are primarily con- 

 cerned with radioactive phenomena, such as 

 the rate of emission of energy and the rate of 

 production of alpha particles. In problems be- 

 longing to the fcst class we are concerned with 

 the total amount of material present; but in 

 problems of the second class we are directly 



concerned with only the relatively small frac- 

 tion iXjSf) of the atoms present that take part 

 in the phenomenon studied; we are only in- 

 cidentally interested in the atoms that have 

 remained untransformed. 



In such problems, comparable amounts of 

 different radio-elements are such as correspond 

 to the same value of \N. There should be a 

 name by which to denote the amount of any 

 radio-element, irrespective of family, that is 

 thus comparable to a gram of radium. If, 

 tentatively, we use the letter r to denote this 

 quantity, then an r of any material may be 

 defined as that amount of the material that 

 will produce transformed atoms at the same 

 rate as transformed atoms are produced by 

 one gram of radium. This quantity plays in 

 radioactivity a part that is analogous to that 

 played by the gram-molecule in physical chem- 

 istry, and the adoption of some name for it 

 will facilitate the recording, discussion, and 

 presentation of observations and phenomena. 



Thus arises the question whether the term 

 " curie," which denotes an r of radium emana- 

 tion, shall be redefined so as to cover the entire 

 field embraced by our definition of the quan- 

 tity r, or whether a new name shall be added 

 to the nomenclature of the science. This 

 question was submitted by the Bureau of 

 Standards to a number of chemists and physi- 

 cists; the majority of those who replied fa- 

 vored a redefinition of the " curie." 



The advantages to be secured by adopting a 

 name for the quantity here denoted by r 

 are considered in greater detail in an article 

 that will appear in an early issue of the Jour- 

 nal of the Washington Academy of Sciences. 

 ISr. Ernest Dorset 



Bdrean of Standards, 

 Washington, D. C, 

 July 30, 1921 



THE VALUE OF TILTH IN AGRICULTURE 



To THE Editor of Science: If the surface 

 of the earth be broken up to a moderate depth, 

 the growth of plants will be marvelously in- 

 creased, as has been known from time im- 

 memorial. 



A scientific explanation of this fact is sug- 



