MINUTES OF SECTION A. 



May II, 191 1. — Albert S. Barker spoke on "Polariza- 

 tion of Light," illustrated by diagrams and apparatus. 



May 18, igii — C. Edgar Ogden showed an Indian imple- 

 ment of trap, probably used for polishing, from Black Horse 

 hill ; also a very fine arrow head of clear flint from Swarth- 

 more. C. M. Broomall reported that his bacterial investiga- 

 tion of Media water showed improvement in quality. Sanford 

 Omensetter announced the appearance of red rust on berry 

 plants and the advent of night flying moths. 



May 25, 1911. — T. Chalkley Palmer by blackboard dia- 

 grams illustrated the mechanism of motion in diatoms. San- 

 ford Omensetter exhibited specimens of Drosera. C. M. 

 Broomall remarked upon the bacterial purity of Media water 

 the past few weeks. He also spoke of the alternations of 

 shape assumed by drops in falling from a faucet. 



June 8, 1911. — Address, "Photometry," by Dr. Harold 

 C. Barker, illustrated by apparatus and formulas. 



June 15, 1911. — T. Chalkley Palmer spoke on Navicula 

 socialis, illustrated by blackboard diagrams, and advanced the 

 hypothesis that the groups of four in that species originate 

 in a tetraspore. C. Edgar Ogden gave an account of the 

 geology of a recent trip to Reading, Pa. In answer to a 

 newspaper statement that seventeen year locusts were due 

 this year, Sanford Omensetter replied that they could not be 

 expected for eight years yet. CM. Broomall by blackboard 

 illustration controverted the theory of the constant tendency 

 of cooling materials to crystallize in six sided figures. A. S. 

 Barker spoke of having at one time seen globular lightning. 



June 22, 1911. — Sanford Omensetter reported the advent 



