A P'EATURE OF MAYON VOLCANO 



2«I 



sine curve. As a rule, however, the height of the summit of 

 these mountains above the camera is not known, and there is 

 insufiicient proof that the camera was properly leveled. It is 

 to be wished, in the interest of vulcanology, that observers tak- 

 ing photographs of such cones would carefully level their instru- 

 ments and state the exact locality from which they were taken, 

 in order that when the topography of the regions is better 



Fig. I. 



known, it may be possible to determine exactly what the value 

 of c is for each particular case. 



Closely allied to the form of volcanic cones is that of the 

 small "driblet cones" of J. D. Dana. He describes them as 

 forming about small apertures whence the escape of vapors 

 produces a throw of fiery spray. The drops fall back upon 

 one another, becoming soldered, because still partially melted, 

 and gradually build up the driblet cone.^ He was able to ob- 

 serve the process in Hawaii. 



While in a cone of the Fuji type the solid ejecta falling on 

 the steep slopes must roll or slide down the declivities to a 

 greater or less extent, it is possible to imagine the several par- 

 ticles so sticky as to stay where they fall and this seems actually 

 to be the case when driblet cones form. The drops from a 

 vertical spray, or the grains from a vertical sand blast of small 



1 Characteristics of Volcanoes, 1890, pp. 17, 71, 85, 160. 



