500 



THE NATIONAL GEOGRAPHIC MAGAZINE 



Photo by J. Fid Tristan 

 CLIMBING OUT O^ POAS 



himself — there is no seasonal periodicity, 

 the seisms being distributed almost evenly 

 throughout the twelve months. 



The quakes very seldom come singly, 

 but mostly in groups, with one or several 

 culminating shocks at some point of the 

 series. In the i888-'89 series, of which 

 the writer made a special investigation, 

 the phenomena began October ii, 1888, 

 with almost imperceptible trepidations, 

 and continued to increase until December 

 30, at 4.12 a. m., when a destructive 

 shock worked havoc in San Jose and in 

 the neighboring towns, and then steadily 

 diminished, finally en^'ing on February 

 18. _ The total number of separate shocks 

 registered by the instrument was 45. 



Notwithstanding the fact that in the 

 minds of the highly imaginative and ex- 

 cited natives the volcanoes were the 

 original cause of the disturbance, these 

 hardly showed any unusual activity, as 

 was made clear by a careful explora- 

 tion; but this failed to satisfy the pub- 

 lic, and the responsibility was speedily 

 shifted to a hitherto unheard of crater. 



the Cacho Negro, which gave 

 the investigating commis- 

 sioner more trouble and head- 

 aches than all the real vol- 

 canoes and earthquakes taken 

 together. 



THE ERUPTION OF PDAS, JAN- 

 UARY, 1 910 



In the most recent happen- 

 ings, the disturbances seem to 

 have started with a colossal 

 eruption of the Poas geyser 

 on January 25 last. On that 

 day, at about 5 p. m., an ex- 

 traordinary smoke-like column 

 was seen from San Jose rising 

 to a prodigious height, which 

 the scientific commission, ap- 

 pointed later to investigate the 

 volcano, estimated at no less 

 than 13,000, feet. After reach- 

 ing its higher point, the col- 

 umn spread into a mushroom- 

 shaped grayish cloud, which, 

 carried by the anti - trade 

 winds, soon covered like an 

 immense screen the whole valley of San 

 Jose. 



An hour after the first indication of 

 the unusual phenomenon, a rain of ashes 

 or volcanic sand began to fall in the 

 capital, situated at about 20 miles, as the 

 crow flies, southwest of Poas. Travel- 

 ing in the direction toward the latter, it 

 was noticed that the sand increased in 

 quantity as well as in the size of its 

 grains. 



In the near proximity of the crater 

 the volcanic mud was strongly mixed 

 with stones, many of which, measuring 

 as much as 1.3 foot in diameter, had 

 broken in their fall thick limbs and roots 

 of trees and penetrated deep into the 

 ground. The geyserian crater itself had 

 resumed its usual placidity, its eruptive 

 manifestations even seeming to have 

 stopped altogether. 



From his practical knowledge of the 

 usual course of events, the writer sur- 

 mises that from the date of the above- 

 described eruption there were repeated 

 earth tremors in the surrounding region, 



