PERCY QUKNSEL 



li-. 



uial weathering of basalt. Bahia Cumberland, Masaticrra. Photo C. Skotisbci^;. 



Oiiantities of pyroclastic material are found interbedded between the lava 

 Hows all over the island. Pohlmann has described such products from Bahia 

 del Padre as follows: "Uberall sieht man Decken von basaltischem, meist saulen- 

 formi^ abj^esondertcm P'.ruptiv^estein mit Schichten von vulkanischem Auswurfs- 

 niaterial wie Asche, Lapilli, l^omben u. s. w. wechsellagernd. 



Mine solchc aus Lapilli und l^omben zusammengesetzte Schicht von mehreren 

 Mctern Maclitij^keit an der rechten Seite der Bucht in der Nahe der sog. Kapelle 

 <;elc^fen, liefcrt das Material der sog. 'Glockensteine', Der Vorgang ihrer l^ildung 

 ist, kurz gcsagt, folgendcr: zuniichst entstehen traubige und nierformige Con- 

 crctioncn zwischcn den losen zusammengefiigten vulkanischen Massen; dieseweissen 

 Knollen (JMg. i 2) gelangen beini Abstiirzen der Schichten an den Strand und erhalten 

 als Kollstcinc (lurch die Thiitigkeit des Wassers ihre gerundete P'orm" (lO, p. 321). 



I ha\e prc\i<)us]y noted that the lava beds of the eastern parts of the island 

 are also often interbedded with agglomeratic layers (12, p. 257). 



Some stra>' occurrences of superficial tuffs seem still to have evaded destruction 

 by erosion. Wlu-n Kcnard says that "amongst the specimens collected at Juan 

 I'"cnian(iez (Masaticrra) !)>• the Ciiallenger l^x|)edition in 1 875, we have not found 

 any specimen which iniglit belong to any recent eruption, no tuffs, no volcanic 

 ash are to be found and e\cr\thing seems to prove that they have been washed 

 away by the waves and the atmosj)heric agencies" (8, j). 176), this last conclusion 

 seems (juestionable. 1 lagerman refers to two specimens in Skottsberg's collections 



