18 IOWA ACADEMY OF SCIENCES. 



fields of knowledge thus brought to view he has new experiences and new 

 thoughts and is taught the increased importance of application, reasoning 

 and preliminary training. In short we aim to benefit first the student and 

 next the profession by the second kind of experimental work. 



The time spent on thesis investigation and writing ranges in amount 

 from one hundred to two hundred hours of actual work. 



The scope of the original work in experimental engineering for the past 

 two years is indicated by the following subjects chosen from the whole 

 number assigned: 



Thejorce exerted in cutting cast iron, wrought iron a7id steel in the lathe. — 

 For cast iron the force is proportional to the amount of metal removed. For 

 wrought iron and steel the force does not increase as rapidly as the amount 

 ot metal removed. 



Determination of the point pressure and twisting 7noment exerted by twist 

 drills in cast iron, steel and brass. — A collection of data useful in the design 

 of drill presses. 



The resistance of swing check valves in the return pijyes of steam heating 

 systems.— ¥o\in& to be very slight, indeed — not over one-quarter of a pound. 



Some of those projected for the coming year are: 



Friction of cylinder oils. 



Variatio7% of stress in the jiunching of metals. 



Variation of economy of the steam engine with change oj load. 



Experitnents with small venturi meters. 



In the other departments of the engineering, electrical, civil and mining, 

 the experimental work plays an important part and is prosecuted with 

 vigor by the instructors and students. 



Ames, Iowa, December 26, 1893. 



ON THE GEOLOGICAL POSITION OF BENNETTITES DACOTENSIS 



MACBRIDE, WITH REMARKS ON THE STRATIGRAPHY 



OF THE REGION IN WHICH THE SPECIES 



WAS DISCOVERED. 



BY SAMUEL CALVIN, IOWA CITY. 



Since Professor Macbride's paper on Bennettites dacotensis was published 

 in the American Geologist for October, 1893, there have been numerous 

 inquiries respecting the exact geological horizon from which the cycads 

 were derived. The close resemblance and the intimate relationship indi- 

 cated between the Dakota fossil and Tysonia marylandica Fontaine, 

 while not conclusive, would point toward a common horizon for the two 

 species, and so make it possible to correlate the Potomac formation with a 

 definite Mesozoic horizon in the northwest. Prosessor Macbride's paper left 



