IOWA ACADEMY OF SCIENCES. 47 



No. 1. No. 2. 



Weight of powder... 5882 gram. .4559 gram. 



Si O2 found 95.53% 96.14% 



Al 2 O3 plus traces of Fea O3- 4 59% 4.01% 



Total 100.12 100 15 



The force of adhesion to a wet surface was estimated at 200 

 grams per square centimeter, or about one -fifth of an atmos- 

 phere, but it may be much greater. If applied to a poisoned 

 wound at once it would undoubtedly absorb some of the poison 

 and so assist in the cure. The popular belief in its efficacy has 

 therefore, some foundation in fact. 



If more of this rock can be secured it is our intention to test 

 the rapidity of its absorption of moisture from the air when cut 

 in thin slices, with a view to its use as a hygrometer. 



The vein in which the specimen was found is twenty feet 

 wide, nearly vertical, and strikes westward. The contents of 

 the vein are chiefly light and dark blue translucent quartzite, 

 mixed with amorphous clay and iron oxide, and bordered by a 

 thin blanket of limestone. Some of the translucent quartzite 

 is mixed with light gray mad stone, as if the firmer portions 

 were formed by fusion of the light gray material. The latter 

 agrees very closely in composition, as well as in appearance, 

 with the silicious shells already mentioned, and was probably 

 formed from them by the internal heat of the vein. 



PHYSICAL THEORIES OP GRAVITATION. 



T. PROCTOR HALL. 



A force which belongs to individual atoms, is independent 

 of chemical and physical conditions, and cannot be altered or 

 destroyed by any known means, must be closely related to the 

 fundamental nature of the atoms. One of the most essential 

 parts in our concept of matter is mass, and the force of gravi- 

 tation of an atom is proportional to its mass. Mass and gravi- 

 tation stand, therefore, either as co-effects of the same cause or 

 as cause and effect. The force exerted by each atom at any 

 point decreases in proportion to the increase of the expanding 



