46 IOWA ACADEMY OF SCIENCES. 



specimens were secured as a curiosity, and after being properly- 

 rounded, to obscure their origin, were recognized by some of 

 the "old inhabitants" as genuine mad stones. Their curative 

 power has yet to be tested, but in all other respects, apparently, 

 their identification is complete. 



The fragments removed from the larger specimen were pre- 

 served for examination and analysis. The specimen itself is 

 larger than a hen's egg, light gray in color, with darker specks 

 of iron scattered through; distinctly stratified; with no cleavage 

 planes. The luster on a broken surface is resinous, on a worn 

 surface more earthy. Its hardness, considered as a rock is 2i, 

 but the fine powder scratches glass. It is infusible in an ordi- 

 nary blowpipe flame, and powders easily after ignition. 



Under the microscope it appears to be made of flat and irreg- 

 ular transparent granules about 1-500 millimeter thick, some of 

 which are ten times that width, fitted loosely together so as to 

 leave irregular cavities everywhere in communication with each 

 other. The fragments resemble fragments of silicious infuso- 

 rial shells which are found in large quantities in some parts of 

 the Rocky mountains. 



The specimen after remaining some weeks in the air of a dry 

 toom (heated by hot air) weighed 70.77 grams. It was placed 

 in distilled water, in which it floated for two or three minutes, 

 boiled for some hours, and allowed to cool. After weighing it 

 was hastily dried with a piece of filter paper and weighed 

 again. Lastly it was dried some hours in an oven at a temper- 

 ature of 100^ to 150° C, cooled in a desiccator, and weighed. 



Weight in ordinary dry air... 70 77 grams. 



Weight in water, saturated 39.14 grams. 



Weight in air, saturated 115.00 grams. 



Weight in air, dry 69.15 grams. 



From this data we get: 



Volume of rock in the specimen 30 01 cc. 



Volume of cavities in the specimen 45.85 cc. 



Total volume 75.86 cc. 



Specific gravity of rock 2.304 



Specific gravity of the whole .912 



Volume of water held in ordinary dry air. 162 cc. 



Some fragments of the stone were pulverized in an agate 

 mortar, fused with sodium and potassium carbonates, and 

 analyzed in the ordinary way. Before fusion the powder was 

 dried at about 150^^0. The results are as follows: 



