4 Journal of the Mitchell Society [December 



weather out-door humidity is apt to be below what it should be for 

 satisfactory manufacture. 



"With exception of textile fibres, the curves for moisture content 

 of various materials with reference to atmospheric conditions have 

 not been determined. 



The various commercial methods of humidification were men- 

 tioned and briefly described, and the Bahnson Humidifier was dem- 

 onstrated under actual operating conditions. 



249th Meeting— May 10, 1921 



Archibald Henderson — The Lorentz Transformation in Einstein 



Relativity. 



Dr. Henderson attempted to give in the simplest possible mathe- 

 matical terms the explanation of the Principle of Relativity (in the 

 restricted sense), following the lines worked out by Einstein himself. 

 After deriving the equations of the Lorentz transformations, Dr. Hen- 

 derson gave their mathematical interpretation (1) The systems are en- 

 tirely symmetrical; (2) A beam of light must have the same velocity, 

 when viewed in the variables of either system; (3) The equations for 

 low velocities reduce to the Newtonian equations; (4) A meter-stick 

 perpendicular to the direction of motion remains constant. Analyz- 

 ing these equations further, Dr. Henderson showed the interdepen- 

 dence of time and space which they present, so that the phrase 

 "points" in "space" is replaced by the expression "events" in "the 

 world." The in variance function was interpreted as indicating a 

 "rotation" in four-dimension Euclidian space with imaginary time- 

 axis; or else, a "rotation" in four-dimension non-Euclidian space 

 with real time-axis. It was pointed out that the Einstein theory of 

 Relativity raises the deepest questions regarding space, time, gravi- 

 tation, and the essential characteristics of the physical universe. 



W. C. CoKER — Effect of Length of Day on Growth and Reproduction of 



Plants. 



A review was given, illustrated by lantern slides, of the highly 

 significant work of Garner and Allard on this subject. Mr. Allard 

 was assistant in botany in this University sixteen years ago and went 

 from here to the Department of Agriculture in Washington, where he 

 is still working. In an extended series of experiments with growing 

 plants the authors have shown that the length of day, that is the time 



