Record. xli 



Dr. Wm. Trelease — Four rosaries made from seeds by the Alaska 

 Indians. Two pouches of sealskin (the hair seal or blubber seal), 

 made by the Alaskan Coast Indians. An Aleutian waterproof jacket 

 and belt, made of seal intestine. Relaxed by wetting these are 

 worn, the belt tightened about the waist and about the rim of the 

 bidarka or kayak — a skin boat. 



Dr. A. S. Pearse gave an illustrated talk on "Fiddler 

 Crabs." 



Mr. Phil Rau read a paper on "The Life History of 

 the Devil Horse {Stagmomantis Carolina). ^^ 



The death of Mr. J. J. Cole was announced. 



June 3, 1912. 



President Engler in the chair; attendance 25. 



Dr. Wm. Trelease presented to the Academy a paper 

 weight — the original punch for the Engelmann medal on 

 the occasion of the semi-centenary of the Academy. 



Professor F. E. Nipher addressed the Academy on 

 "Electric Waves in Solid Conductors." 



Dr. Robert J. Terry presented some results of his 

 work on "The Development of the Cranium in Mam- 

 mals." 



Professor J. L. Van Ornum spoke on "The Effect of 

 Fatigue Tests and of Moisture Upon the Elasticity of 

 Concrete." 



Six years ago the Civil Engineering Department of Washington 

 University made an extensive investigation of the effects upon con- 

 crete of repeated loadings, the number of repetitions generally run- 

 ning well into the thousands. Pertinent to the discussion of this 

 evening, that of "The Effect of Fatigue Tests, and Moisture Upon 

 the Elastic Properties of Concrete," are conclusions then reached 

 that, if the intensity of the repeated load exceeded about half the 

 ultimate strength of the concrete, the Modulus of Elasticity con- 

 tinually decreased after the first repetition until it became exceed- 

 ingly small just before failure; and if the repeated load was less 

 than the intensity just mentioned, the modulus decreased at first 

 but rapidly approached a constant value of about two-thirds the 

 maximum, and the failure of such specimen did not occur. These 

 experiments were of service in enabling a satisfactory fixing of 

 the equivalent elastic limit or yield point of concrete and so arrive 

 at safe working stresses in design. 



The particular experimental investigations now reported by Pro- 

 fessor Van Ornum, as abstracted from a graduation thesis of a year 



