68 Transactions Tennessee Academy of Science. 



Diffraction PKenomena Due to the Dimensions of the 

 Source of Light 



By Brown Ayres, University of Tennessee. 



(Abstract.) 



A diffraction phenomenon of great beauty is produced by pass- 

 ing sunlight through a short focus cyHndrical lens and then 

 through a scj[uare mesh gauze. The disturbing action of the ap- 

 parent diameter of the source of light as seen from the guaze 

 causes the disappearance of the shadows in the plane perpen- 

 dicular to the cylindrical lens. The mathematical theory is of 

 great complexity and difficulty. At a moderate distance from the 

 gauze the appearance is that of a brilliantly colored cloth. Farther 

 away the regular spectra are seen within and without the geomet- 

 ric shadow of the wires. 



The Green Slates of Georgia 



By T. Poole Maynard. 



(Abstract.) 



The green slates of Georgia are the only known commercial 

 green mica slates occurring south of Vermont. They occur in 

 Bartow and Gordon Counties and are found in the Connasauga 

 formation of Cambrian Age. The Connasauga formation at- 

 tains a thickness in Georgia of 2,000 feet, and is made up of 

 shales, slates and limestones. The slates are found in this for- 

 mation only where all conditions of sedimentation and local meta- 

 morphism have been suitable for the changes to take place. In 

 places the slates are found where quarries can be worked over a 

 wi(hh of 250 feet, length of four to five hundred feet and to any 

 (k'litli comnicrcially ])Ossible. 



