202 The Philippine Journal of Science ms 



Until the year 1863 nothing was written on Philippine earth- 

 quakes. 2 Even at the present time there exist but few papers 

 based on modern seismologic principles, and all of these have 

 been written during the last ten years. 



The Manila Observatory from its foundation as a private 

 institution in 1865 has directed its attention to earthquakes, but 

 for many years its work was confined to segregating and publish- 

 ing exact monthly observations without making a complete study 

 of the subject. Its collection of monthly curves in which are 

 contained the hourly observations of the Bertelli microseismo- 

 graph is exceedingly valuable on account of the long period of 

 time covered. 



The earthquake of June, 1863, which practically destroyed 

 the city of Manila and many of the neighboring towns and 

 caused the death of more than 400 persons, led to the nomination 

 of a commission to investigate the architectural character of the 

 buildings and the nature of the soil of Manila in so far as these 

 might be a source of danger in the future. As at that time the 

 only engineers in the Philippines were those who were members 

 of the corps of military engineers, the commission was formed 

 from among these, but their work appeared to be limited to the 

 establishment of several more or less successful principles and 

 practical rules to which the plans of the new buildings to be 

 erected in Manila were to conform. 



Ten years later the commander of military engineers, D. 

 Mariano Cortes y Aguillo, wrote a memoir on the same subject. 8 

 Notwithstanding the undoubted merit of this work as a practical 

 guide for architects, little account was taken of it by the author- 

 ities, and it was not published until after the earthquakes of 

 1880. The author discusses the different seismic theories with- 

 out adopting any of them regarding Philippine earthquakes. 

 He concluded, after the examination of the damaged buildings 

 and other existing data, that the most violent seismic movements 

 in Manila are in an approximate north and south direction. 



After the earthquakes of 1880, a commission composed of 

 engineers of public works was appointed to study with care 

 the ruins caused by these earthquakes, to point out the defects in 

 the structure of the buildings that had been damaged, and to 



3 The more or less accurate accounts of earthquakes which may be found 

 scattered in the histories of the Philippines are not here considered. 



* Los terremotos — Sus efectos en las edificaciones y medios practicos para 

 evitarlos en lo posible. Manila (1881). 



