December 17, 1915] 



SCIENCE 



851 



exist between these two properties may be 

 quite obscured by the different impurities. 

 This is what generally happens when dif- 

 ferent people study the properties of vary- 

 ing samples. 



One of the most recently undertaken of 

 all these investigations is the study of sur- 

 face tension of these same organic liquids. 

 Surface tension, as you well know, is that 

 tendency (caused doubtless by the cohe- 

 sion of the molecules of substance) which 

 forces any liquid surface to contract as 

 much as possible, thus making drops and 

 bubbles spherical, and drawing liquids up 

 in capillary tubes. Surface tension is of 

 peculiar interest in relation to the theory 

 of compressible atoms, because it gives 

 another clue to the cohesive forces holding 

 matter together in the liquid and solid con- 

 dition; but the published data even for 

 such a common substance as water vary 

 widely, often as much as 10 per cent. 

 Hence the more careful study of this im- 

 portant property formed a legitimate part 

 of the scheme of investigation for which 

 the Wolcott Gibbs Memorial Laboratory 

 was planned. In the first year of this re- 

 search, which is being continued at the 

 present time, we were able to find most of 

 the important causes of the serious diverg- 

 ences in earlier work. Many of the experi- 

 menters had immersed their capillary 

 tubes (in which the effect was to be meas- 

 ured) in other tubes much too narrow for 

 the purpose, not realizing that even a tube 

 one inch in diameter causes an appreciable 

 "capillary" rise of the liquid contained 

 within it. Again, they failed to allow for 

 optical imperfections in the glass of the 

 tubes containing the liquid, their methods 

 of measurement were sometimes inade- 

 quate, and the mathematical formulffi used 

 for calculating the results were often 

 faulty. Therefore, in our preliminary 

 work, which was reviewed briefly in the 



July number of the Proceedings of this 

 academy, it is hoped that a distinct ad- 

 vance has been made. 



If high quality had not been sought, of 

 course the number of investigations could 

 have been much greater. Some one has 

 wisely said that the output of physico- 

 chemical work is inversely proportional to 

 the square of the grade of accuracy de- 

 sired. In the brief space of these few min- 

 utes it has been impossible to give much 

 more than a mere list. Those of you who 

 are specially interested will find many of 

 the researches already published in full; 

 brief accounts of others are in the Year 

 Books of the Carnegie Institution of 

 Washington, and before long it is hoped 

 that the rest also may be printed. 



An investigator for whom much has been 

 done feels gravely the responsibility which 

 rests upon him of doing much in return; 

 and although in this case he feels the neces- 

 sary human inadequacy and incomplete- 

 ness of the work just described, neverthe- 

 less he hopes that at least a beginning of 

 accomplishment has been made, and that 

 in the future the Wolcott Gibbs Memorial 

 Laboratory, through many years, will 

 yield ever increasingly useful additions to 

 the sum of human knowledge. 



Theodore W. Eichaeds 



Hakvaed University 



TEE LIFE OF RADIUM 

 The life of radium, or the length of time 

 required for a given quantity of radium to 

 be transformed and converted into other 

 elements, is a physical magnitude of con- 

 siderable importance and interest. Its 

 chief significance lies perhaps within the 

 special field of radioactivity where radium 

 occupies a unique position in being the only 

 highly radioactive radio-element which pos- 

 sesses physical and chemical properties, 

 and occurs in a sufficiently high state of 



