MATEBIAI-S FOR COXCRETK CONSTRUCTION IN MANILA. 475 



sliapes of and the absence of partially developed fractures which are 

 found in the small sizes of crushed stone. 



Thus far there has been accumulated only a small amount of data 

 concerning the efficiency of Pasig gravel. In crushing concrete cubes, 

 Mr. Eeibling found that in several cases the gravel was weaker than 

 the mortar. In one cube 40 per cent of the gravel broke. 



CEUSHED STONE. 



Sources. — The only large commercial cjuarry near Manila is situated at 

 Sisiman, near Mariveles, at the entrance to Manila Bay. This point is 

 so distant that considerable expense is required for transportation, never- 

 theless a large amount of the stone has been used in Manila for concrete 

 construction. There are other quarry sites near Sisiman, some of which 

 show a better stone and there are pilaces which are better protected from 

 storms. 



N"ear Los Bancs on Laguna de Bay- a quarry was formerly operated for 

 road material. To obtain stone from this situation a long tow across 

 Laguna de Bay is necessary, and in addition land transportation to the 

 border of the lake is required. 



The city has for some time operated a quarry on Talim Island, but 

 present indications are that the plant will be moved to a better site. 



Under the Spanish regime a quarry was opened in the hills to the 

 southeast of Angono, and a road bed was constructed to the border of the 

 lake and a stone pier built out into the water to enable the dumping 

 of stone from tram cars into scows. Tliis quarry has not been operated 

 recently. To the north of Angono the writer has found a superior grade 

 of rock which the city is contemplating using for macadamizing Manila 

 streets, and it is probable that a quarr)' will soon be opened there. Land 

 transportation will be required for bringing the rock to the lake shore. 



It appears that there are no good quarry sites of hard rock nearer 

 Manila than the vicinity of Angono. C'rushed rock obtained at this place 

 can be brought in small barges which can enter the esteros in Manila and 

 permit of the landing of the material at many places ; this is an advantage 

 since it saves land transportation in Manila. Eock from the Sisiman 

 quarry, or others which might be opened near it, could best be transported 

 on large scows and these, while they could land conveniently on the water 

 front, could not ascend the Pasig Eiver beyond the bridge of Spain nor 

 enter the esteros. 



Nature of the stone. — The Sisiman stone is a gray andesite which in 

 the quarry shows, columnar structure. This structure favors the quarry- 

 ing of large stone. Near by the andesite has a somewhat better texture 

 and is a little harder, and at a few points there is a dark andesitie rock 

 which is superior to the gray andesite, but it is doubtful whether it can 



