MATERIALS FOR CONCRETE CONSTRUCTION IN MANILA. 479 



CONCLUSIOiSr. 



The field work necessary to make known the sources and nature of 

 the sand, gravel and crushed stone available for use in Manila has 

 been completed. An extensive deposit of a superior sand has been 

 discovered in the Orani Eiver and some of this sand is now being 

 used. A new quarry site has been selected for the city near Angono, 

 the stone from which is considerably better than what is now being 

 used from the Talim quarries and is the best obtainable for macad- 

 amizing the streets of Manila and is in every way suited for concrete work. 



The testing of the materials, while incomplete, is sufficient to show 

 their relative efficiencies and to check the conclusions arrived at from the 

 geologic examinations. Further tests extending over longer periods of 

 time and embracing all the conditions which will be met with in practice 

 will be made in the testing laboratory of the Bureau of Science as soon 

 as the facilities will permit. 



The economic problems of the cost of quarrying, dredging and tran- 

 sporting, and the more vital one of obtaining the best results in the use 

 of the materials is beyond the scope of this paper, but some data have 

 been supiplied to assist in their solution. 



Por the tests of materials which are reported in this article the writer 

 is indebted to Mr. W. C. Eeibling, in charge of the cement-testing labora- 

 tory of this Bureau, and to P. D. Eeyes, assistant in the cement laboratory. 



