1918.] NATURAL SCIENCES OF PHILADELPHIA. 73 



The death of George Barrie, a member, January 4th, was also 

 announced. 



Eruptions of the Costa Rican Volcano Irazu in 1917-18. — Dr. 

 Philip P. Calvert stated that the first and greatest known eruption 

 of Irazu occurred in 1723, from February intermittently to December. 

 A contemporary account by the Spanish Governor of Cartago, 

 Don Diego.de la Haya, exists and has been reprinted several times. 



A recent report by Prof. Tristan refers to eruptions of "smoke" 

 or of vapors seen by visitors to the old craters in 1844, 1847, 1855, 

 1859, 1870, 1880, 1884, 1888, and 1910. 



La Informacion, a daily paper of San Jose, for October 6, 1917, 

 published a despatch from a correspondent who visited the craters 

 of Irazii on the preceding day, in which he stated that they were 

 violently exhaling large columns of steam, rising at times to a height 

 of 70 meters, accompanied by sulphurous odors, rumbling sounds 

 and small volcanic stones. 



This notice led Prof. J. Fidel Tristan, accompanied by Senores 

 Alvaro Fernandez Peralta and Ewald Starke to visit the volcano 

 on October 19 and 20, 1917. A report (that alluded to above) by 

 Prof. Tristan and Senor Ricardo Fernandez Peralta on the observa- 

 tioris made on these days was subsequently published in La Gaceta, 

 Diario Official (Official publication of the Costa Rican Government) , 

 for December 4, 1917. It is accompanied by reproductions of some 

 photographs taken by Prof. Tristan and a plan of the craters in 

 eruption. This report has been reprinted in better form as No. 1, 

 Series A, Puhlicaciones, Colegio de Senoritas, San Jose, 1917. 



Professor Tristan found that craters D, E, G, H, L and M (fol- 

 lowing the designations of Dr. Karl Sapper) were discharging vapor. 

 A fuller series of the October photographs than were included in 

 this report has been sent by Prof. Tristan to the speaker, as well 

 as others taken by Senores Jose Maria Tristan on December 19, 

 1917, and Ricardo Fernandez Peralta on December 20, 1917, in 

 the craters, and telephotographs from San Jose by Prof. Tristan in 

 January, 1918. All these photographs were shown on the screen 

 and the speaker added explanatory remarks based on Prof. Tristan 

 and Senor R. F. Peralta's report, articles from various issues of La 

 Informacion and his own visits to the volcano in 1909 and 1910. 

 The later photographs show the chief discharge as being from crater 

 G. A considerable fall of ash and scoriae was reported as occurring 

 on December 19 and January 6 and 7, reaching on the last date to 

 San Jose. 



Samples of the ash collected in San Jose and forwarded by Mr. 

 J. B. Clark, and of ash from the eruption of Poas, of January, 1910, 

 were exhibited under microscopes. The former is much darker 

 than the latter; Prof. Alfaro, director of the National Museum in 

 San Jose, is quoted in La Informacion of January 8, 1918, as saying 

 that the Irazu ash was produced by decomposition of andesite and 

 contained but little sulphur, while that of Poas was due to calcination 

 of pumice and (when first fallen) contained much sulphuric acid. 



The communication was illustrated by lantern views. 



