PUZZOLANIC MATERIALS IN GENERAL. 



633 



torin, tosca, tetin and trass. It may be noted that in origin materials 

 of this class resemble closely the granulated slags used in slag-cement 

 manufacture both volcanic ashes and granulated slags being due to 

 the processes of (1) fusion of a silico-aluminous material, and (2) rapid 

 cooling of the resulting product by ejection into air or immersion in 

 water. The second class includes a number of less important (because 

 less active) hydraulic materials, such as arenes, psammites, etc., which 

 are materials resulting from the decay of certain igneous rocks. 



The principal natural puzzolanic materials will be discussed sepa- 

 rately, in the following order: Pozzuolana (tosca, tetin), trass, san- 

 torin, arenes. 



Pozzuolana. Pozzuolana derives its name from the little town of 

 Pozzuoli, located a few miles west of Naples, at which point the material 

 was first obtained by the Greek colonists, and at a later date by the 

 Romans. The material has also been exploited at other points near 

 Rome and Naples. 



TABLE 234. 

 ANALYSES OF POZZUOLANA FROM ITALY. 



1. Pozzuolana, Rome. Stanger and Blount, Mineral Industry, vol. 5, p. 71. 



St. Paul's Caves. Thoyn, Diet. App. Chem., 3d ed., vol. 1, p. 475. 



Civita Vecchia. Berther, Anal. Gillmon, Limes, Cements, and Mortars, p. 125. 



Naples. Stanger and Blount, Mineral Industry, vol. 5, p. 71. 



" . Stengel, Anal. Zervas, School of Mines Quart, vol. 18, p. 230. 

 Vesuvius. Brown. Thorpe, Diet. App. Chem., 3d ed., vol. 1, p. 475. 

 " " 3d ed., vol. 1, p. 475. 



" Dark gray. " " " " 3d ed., vol. 1, p. 475. 



Light gray. " 3d ed., vol. 1, p. 475. 



10! Lava, Vesuvius, 1868. Thorpe, Diet. App. Chem., 3d ed., vol. 1, p. 475. 

 11. Tuff, Monte Nuova. Merrill, Rocks, Rock Weathering and Soils, p. 141. 



Most of the Italian pozzuolana is obtained from small open cuts, 

 or pits, though some of these workings are now of great depth. Those 

 of Trentaremi, for example, are about 600 feet deep. The various 





