ELISHA MITCHELL SCIEiNTIFIC SOCIETY. 



145 



2. Overton county, Tennessee, blue gray lithographic stone. 



Calcium carbonate 77f^2 



Magnesium carbonate i 7.32 



Iron and aluminum oxide .66 



Silica anil insoluble silicates. _. 4.10 



The specific gravity of both thejse stones is higher than that of 

 the Baravian. and it does not speiu wholly free from crystals. The 

 Clay county stone contains more silica than the Baravian stone, and 

 they both contain more iron. The Overton county stone contains 

 a much larger quantity of magnesium carbonate. For comparison, 

 the following is an analysis of the Bivarian stone : 



Calcium carbonate ._ .- - 81.47 



Magnesium carbonate 13. 83 



Iron oxide .25 



Silicates 4-45 



JAS. LEWIS HOWE. 



Laboratortj of Central University, 



Richmond, Ky., March, 1886. 



CYCLONES. 



In the month of May I witnessed a phenomenon which may assist 

 us in determining the cause or causes of cyclones or tornadoes, and 

 its repeated occurrence under tlie same conditions impressed me 

 with its value to the student of nature and induced the desire that 

 a record of it be preserved. 



In the figure, a is 



the head of a drain 

 pretty well grown up 

 with shrubs and trees 

 in an old field, which 

 supports a not very 

 dense growth of old 

 field pines, the dotted 

 line inn being their 

 northerri border. The 

 drain runs north, and 

 north of the dotted 

 line is cleared land. 



cL 



15 



