474 REPORT OF NATIONAL MUSEUM, 1899. 



5 to 10 per cent of carbon, and equal amounts of iron oxides and 

 varying small quantities of lime. The material has little commercial 

 value. 



4. Madstones. 



These need but brief notice here. The fallacy of the madstone dates 

 well back into the dark ages and perhaps beyond, and strange as it may 

 seem continues down to the present day. Not longer ago than Decem- 

 ber, 1898, the Washington newspapers chronicled the sale for $450 

 of a madstone in Loudovin County, Virginia, and from year to year 

 very man}" letters are received l)y the Smithsonian authorities making 

 inquiries regarding such, or possibly ottering one for sale at fabulous 

 prices. 



So far as the writer is able to learn, either from literature or from 

 personal examination, stones of this class are almost invariably of an 

 aluminous or clayey nature, and their supposed virtue is due wholly 

 to their avidity for moisture — their capacity for absorption, which 

 causes them to adhere to anv wet surface, as the tongue or to a wound, 

 until saturated, when ' they will drop away. It should not be neces- 

 sary to state, at this late day, that their curative powers are purely 

 imaginary. The ancient bezoar stone, used in extracting or expelling 

 poisons, consisted of a calculus or concretion found in the intestines 

 of the wild goat of northern India. ^ 



5. Molding Sand. 



For the purpose of making molds for metallic casts, a fine, homo- 

 geneous argillaceous sand is commonly employed. 



The physical qualities which go to make up a molding sand consist, 

 according to Nason,^ of elasticity, strength, and a certain degree of 

 fineness. It must be plastic in order to be molded around the pattern; 

 it must have sufficient strength to stand when unsupported by the 

 pattern, and to resist the impact of the molten metal when poured into 

 the mold. Too much clay and iron present in the sand will cause the 

 mold to shrink and crack under the intense heat; too little will cause 

 it to dry and crumple, if not to entirely collapse. 



The peculiar virtues of molding sand, as outlined above, are ascril^ed 

 to the fact that each of the sand grains is coated with a thin film of 

 clay. 



The accompanying table will serve to show the varying chemical 

 character of sands thus employed, though, according to authorities 



^ W. J. Hoffman, Folk Medicine of the Pennsylvania Germans, Proceedings of the 

 American Philosophical Society, XXVI, 1889, p. 337. 



^ Forty-seventh Annual Keport of the Regents State Museum of New York, 1893, p. 

 469. 



