﻿432 cox. 



a ball in the dry season to 40 centavos (20 cents, United States currency) 

 during the rains, the higher price being clue to the difficulties encountered 

 in transporting the clay to market. These may be judged from an 

 account of the working of Calamba clay given by Sehor de la Rosa. He 

 says that the clay is dug and carried on the backs of natives about 7 or 8 

 kilometers to the barrio of Bucal where the women make it into balls. 

 When 500 to 1,000 of these are ready they are loaded into bancas and 

 taken about 4 or 5 kilometers to Calamba where they are transferred to 

 a casco and brought under tow to Manila. 



The depth of the kaolin at Calamba has not been investigated, for 

 after digging down about 2 meters it becomes too hot 26 to allow further 

 penetration and then the washing of the rain fills up the hole. The 

 superficial exposure is about a hectare. This kaolin has been used to 

 some extent as a fire clay, for example, to repair the brickkiln at San 

 Pedro Macati and the furnace of the glass factory. Senor Varcena at 

 the school in Sampaloc has made some fire bricks and crucibles of good 

 appearance from this clay. 



As the price of building materials of all kinds is very high and shows 

 little sign of decreasing, the demand for clay products of this nature is 

 sure to increase. Many which are now in use can be replaced entirely by 

 manufactures from local clays, if their preparation is taken up and placed 

 upon a commercial basis. The tests of clays here reported should aid in 

 the selection of suitable localities and in the finding of proper material 

 for the development of these industries. 



RADIOACTIVITY. 



In carrying out a series of experiments to ascertain the cause of the 

 abnormal amounts of radioactive emanations contained in. the air of 

 cellars and caves, it was demonstrated by Elster and Geitel 27 that such 

 emanations were not of spontaneous origin, but rather came from the soil 

 and clay. They proved 28 that the air removed by simple suction from 

 the soil was charged with active emanation and that its activity ac- 

 tually exceeded that of the air of cellars and caves. This activity is 

 either a universal property of the air of the ground independent of 

 the nature of the soil, or it is the result of a certain amount of 

 primarily active substance contained in the material of the soil itself. 

 Elster and Geitel have shown the latter assumption to be the only tenable 

 theory. They found 29 that clay dug from their garden, introduced into 

 their apparatus, after three days had reached a constant maximum value 

 of about three times the normal. They considered that most of the 



20 The Los Bafios springs are thermal. 



"Chem. News (1903), 88, 29. 



a Phys. Ztschr. (1902), 3, 574. 



■° Jbid. (1903), 4, 522; Chem. News: (1903), 88, 30. 



