is,* King: Philippine Concrete and its Aggregates 203 
specimens gave an average result of 1,521 pounds per square 
inch, which is higher than either of the average results obtained 
from the 1 : 2 : 4 or the 1:8:6 specimens made in the field. 
Average results obtained from laboratory-made specimens are 
in each case higher than the corresponding mean values given 
by test pieces made on the building site ; 1 : 2 : 4 results aver- 
age 2,103 pounds per square inch, and 1:3:6 results average 
1,483. Most of the test pieces coming from Laguna were made 
of concrete used in the construction of San Juan Bridge; no 
information was sent to this laboratory regarding the source of 
the aggregate employed in this structure. The 1:3:6 and the 
1 : 2.5 : 5 mixtures gave excellent results, whereas the 1:2:4 
mixture gave only fair values. Laboratory tests made of 
Pagsanjan sand gave excellent results, but the concrete made in 
the field with it (for the construction of the Pagsanjan water 
tank) in one instance gave the very poor strength of 200 pounds 
per square inch. Careless manipulation apparently accounts for 
this extremely low result. 
LEYTE 
Compressive strengths of concrete used in the building of 
Leyte structures are strikingly incongruous, low, and aber- 
rant. Results obtained from 1:2:4 specimens aged 28 to 31 
days vary between the wide limits of 177 and 1,556 pounds per 
square inch. The extremely low average of 177 was obtained 
from three specimens made August 2, 1915, of concrete used in 
constructing Tabontabon School, at Dagami, Leyte. Since the 
Tabontabon River sand used in this concrete is of excellent 
quality, as Table 2 shows, the ridiculously low compressive 
strength is probably due either to faulty manipulation during 
mixing and casting, or to incorrect proportioning of cement, 
or to both causes. There are several other low values in this 
series of 1:2:4 mixtures ; the three specimens from Ormoc 
Market, cast August 19, 1915, gave compressive strengths that 
average 261 pounds per square inch, and those from concrete 
cast September 30, 1915, and used in Tanauan School average 
450. A grand average of the mean values given by the 1:2:4 
specimens having ages between 28 and 31 days gives 907 pounds 
per square inch as compared with 1,989 pounds obtained from 
1:2:4 specimens made at the Bureau of Science August 4, 
1915, of fine beach sand and Baluguhay River gravel. Field- 
made 1:2:4 test pieces aged between 35 and 41 days average 
1,874 pounds per square inch, and those aged between 47 and 
55 days average 1,809, thus showing appreciable increase in 
