Earthquake at the Philippine Isiands. 53 
the Preface says—by ‘los illustrados PP. Jesuitas del Obser- 
vatorio Municipal, 4 quienes nunca se agradeceran bastante los 
servicios prestados al pais en situacion tan angustiosa.” The 
provinces of Manila, Cavite, Bulacan, La Laguna, Pampanga, 
and Nueva Ecija, were the chief victims from the terrible con- 
vulsions ; and, in many parts, their “solid edifices were converted 
into shapeless heaps of ruins, and the materials of their pros- 
perity buried beneath the rubbish.” 
Seismometric observations made at Manila, at the Observatory of 
he “Ateneo Municipal,” from the 14th to the 25th of July, 1880. 
The figures which accompany this Report (see Plate IV) are. 
the records of the seismometer during the principal shocks of 
the earthquake. They were traced by a pendulum six meters 
long, suspended from a point at the termination of four metallic 
rods, and placed within a glass case. The pendulum could 
oscillate freely in all directions, not only under the impulse of 
violent shocks, but also of the slow and gentle undulations 
caused by movements in the walls of the building—to which it 
was rigidly attached. It oscillated over a spherical concavity 
made in a thick piece of wood, whose radius of curvature 
was equal to the length of the pendulum. he concave 
surface was sprinkled lightly with lycopodium powder, to re- 
ceive the tracings made by the pendulum in its various move- 
ments. At the center of the concavity there was a small ring 
which was dragged by the pendulum in its first impulse, and 
which was left at a spot opposite to that from which the first . 
Seismic wave came. ‘This apparatus is that called the horzzon- 
tal seismometer, : | 
of maximum vertical oscillation. 
The object of these instruments is, first, ‘to determine the 
direction of the first horizontal undulation, and this is done by 
means of the ring at the end of the pendulum, which is pushed 
before It on the first impulse; secondly, to find out the general 
direction of the horizontal undulations, and their amplitude, by 
means of the lines traced by the same pendulum in the lycopo- 
dium powder ; thirdly, to ascertain the greatest amplitude of. 
the maximum vertical undulation by means of the index of the 
vertical seismometer ; fourthly, to obtain, by the combination of 
