AN UNUSUAL FORM OF VOLCANIC ELECTA 453 



in the tuff appears near the center of the photograph. The broken 

 surfaces display clearly the concentric structure which is charac- 

 teristic of these bodies. The balls can be disintegrated between 

 the fingers when wetted, and the individual particles prove to be 

 like dust in size. That these aggregates have not resulted from 

 solution processes nor from dynamism is evidenced by the facts 

 that they do not contain calcium carbonate nor any other extra- 

 neous cementing agent, and that the beds in which they occur have 

 certainly not experienced metamorphism. The theory which 

 Dr. Hovey advanced to explain the presence of "drops of mud" 

 in the ejecta from Mont Pelee accounts satisfactorily for the 

 similar, although apparently smaller, balls of dried mud in the 

 loose tuffs of southwestern Luzon. 



W. H. Brown, botanist, Bureau of Science, has submitted to me 

 several hundred balls of dried mud which he found included "in 

 the upper part of a thick bed of volcanic tuff" on the slopes of 

 Mount Maquiling, an extinct volcano about 20 kilometers north- 

 west of Taal. He had been engaged in a study of the flora of 

 Mount Maquiling and had encountered these balls in the course 

 of a soil survey. They are precisely like those already described 

 in shape and structure, but many of them are larger and they 

 have a brownish-yellow color, whereas the Taal products are light 

 gray in color. They consist of the same material as the inclosing 

 bed — clayey, fine-grained tuff. The balls from Maquiling attain 

 a diameter in rare specimens of as much as 4 centimeters, thus 

 being comparable in size with the drops of mud observed by 

 Dr. Hovey, and are so hard that they can be broken only with diffi- 

 culty between the fingers. The appearance of a face in the tuff bed 

 containing these balls is shown in Fig. 3. The concentric structure 

 of the balls is again revealed in this photograph. 



Recently, also, I have encountered well-preserved balls inclosed 

 in clayey tuff on Bondoc Peninsula, Tayabas Province, and near 

 the Santa Lutgarda iron mine at Angat, Bulacan Province, widely 

 separated parts of Luzon. The tuff beds in these localities are of 

 greater age than the recent tuffs in the Taal volcanic region, 

 dating back, probably, to the late Miocene. The tuff is slightly 

 indurated, but the balls have retained their form and display 



