XI, A, 5 Witt: Philippine Paving-brick Materials 207 



building for which is now being erected in Santa Cruz, None of the clay 

 deposits of Laguna Province have been thoroughly studied up to the present 

 time and, therefore, I vsdll first discuss those so situated that the stripping 

 of the material would entail the least labor and the soil overlying could 

 easily be disposed of. Such clays would be economical to use were they 

 of high grade. 



The work consisted in accurately locating a number of clay 

 deposits and in examining their chemical and physical properties. 

 It was found that — 



all of the high grade clays of Laguna Province are more or less mixed with 

 clay of poorer quality. It is a question what percentage of the mixture 

 is useful and whether the expense of sorting will not be so great that it 

 can not compete with kaolin from other sources. 



Adams and Pratt * give a report on the pottery industry in 

 the Philippines up to 1910. This paper contains considerable 

 information on the crude processes in use for making pottery, 

 the general equipment, and other points of interest. The authors 

 visited a number of potteries and brick factories. 



The usual type [of kiln] is a long semicylindrical structure built on a 

 grade of about 10 per cent, having a chimney at the upper end and a door 

 and hearth at the lower. There are also openings for firing along the 

 sides of the kiln. They are constructed of volcanic tuflf and common brick 

 laid up and plastered over with mud. The fuel used is wood. A high 

 temperature can not be obtained in these kilns and the semivitrified 

 products from some of them are due to the low fusing point of the clays 

 used. There is considerable shrinkage in burning, and when the clay 

 fuses the sand used to prevent cracking comes to the surface, making the 

 ware rough and pebbly. 



A study of Philippine clays in relation to pottery manufacture 

 has been made by Crowe,'' of the Philippine School of Arts and 

 Trades. 



The papers mentioned above are the only ones published so 

 far by the Bureau of Science in which the properties of Philip- 

 pine clays are considered directly in connection with ceramics. 

 However, papers have appeared on Portland cement raw mate- 

 rials * which deal with clays and shales. 



•Adams, G. I., and Pratt, W. E., This Journal, Sec. A (1910), 5, 143. 



'Crowe, C. H., Trans. Am. Cer. Soc. (1912), 14, 723. 



' Cox, Alvin J., Philippine raw cement materials. This Journal, Sec. A 

 (1909), 4, 211. 



Reibling, W. C, and Reyes, F. D., The efficiency of Portland cement 

 raw materials at Naga, Cebu, ibid. (1914), 9, 127. 



Pratt, W. E., Geological and field relations of Portland cement raw 

 materials at Naga, Cebu, ibid. (1914), 9, 151. 



