An attempt will be made in the following paper to bring together, so far as is practicable, all that is known of the geology of the Philippine Islands. The report is intended as a vade mecum for geologists in the field and a guide to the literature in the office. Doubtless something has escaped which should have been included, especially among the shrewd remarks of early Spanish travelers, but research in that direction is curious rather than profitable. If here and there they caught a glimpse of truth, with which it would be pleasant to credit them, most of their views on geological matters were of a grotesque falsity, with which it would be unkind to reproach them.