-60 JOURNAL OF THE [April, 



Mobile County. A full analytical study of the same has been 

 made for the Alabama Report on the Tertiary. 



" The sand has a greater specific gravity than common silicious 

 sands. By the passage of a small magnet, crystalline grains of 

 magnetite and magnetic spherules may be isolated, and when a 

 portion of the sand is spread on a glass slip, and gently tapped 

 to reject all grains which do not adhere, many perfect crystals of 

 silex will be found, showing minute crystalline inclusions, gase- 

 ous or other vacuoles, and the characteristic colors of the true 

 gems when examined by polarized light. The use of the green 

 glass slips accompanying these packets differentiates the angles, 

 edges, apices, gaseous vacuoles, and minute crystalline inclusions 

 of these grains, in beautiful pink or rose-colored hues against 

 an emerald-green ground. 



"5. A packet of curious silicious bodies, designated by Dr. 

 Ehrenberg as ' Phytolitharia,' to each of which he gave a specific 

 name in his ' Micro-Geologie,' as if they possessed the same 

 interest as the diatoms and rhizopods usually associated with 

 them. 



" These are examined by spreading a thin layer in a dried state 

 under condensed surface illumination, when the characteristic 

 features of each will be noted. If mounted in balsam the stereo- 

 scopic character is lost, as all the cylinders, etc., appear flat and 

 of little interest. The differentiating power of the polariscope is 

 well shown on a balsam-mounted slide of these ' Phytolitharise.' 

 A few scattering grains of silicious sand and micaceous scales 

 respond to the polarizing power, glowing with prismatic colors, 

 but not one of all the various forms of ' Phytolitharia.' These 

 * Phytolitharite ' are derived from a stratum of swamp clay at 

 Whistler, Alabama, and also from a stratum of bluish plastic clay 

 containing a long series of plant and animal remains, i.e., diatoms, 

 rhizopods, spongilla spicules, plant capsules, and spores in endless 

 profusion." 



OBJECTS EXHIBITED. 



1. The Alga as scraped from trees : by Carlton C Curtis. 



2. Longitudinal section of young thallus : by Carlton C. 

 Curtis. 



3. Longitudinal section of sporocarp : by Carlton C. Curtis. 



