Ferret — Representation of Volcanic Phenomena. 55 



parts of the mountain are gravitationally transported to lower 

 and more peripheral resting places, forming hot ash flows, if 

 of freshly erupted substances and, in any case, dry avalanches, 

 of which a variation is constituted by the equally imposing, 

 but often less directly observable, inter-crateric slides. If 

 these last are of considerable magnitude, the result may be an 

 external ash cloud greatly resembling those due to explosion, 

 and it is important that the two should not be confounded. 

 "With the advent of water the translocation is effected by the 

 mud lavas which so frequently form a highly destructive 

 adjunct to an eruption. The diagram key terminates with the 

 item of true landslides, of volcanic causation, which have been 

 frequent in Japan. 



In illustration of this diagrammatic method, twelve exam- 

 ples are reproduced on Plates I to IV (two-thirds size) a glance 

 at which will be more explanatory than many pages of descrip- 

 tion. Attention is called to the comparison of the consecutive 

 outbreaks of Stromboli and their contrast with the effusive 

 eruption of Etna; to the still greater difference between the 

 extreme types Kilauea and Krakatoa ; and to the phase varia- 

 tions in the progress of the great Vesuvian event of 1906, for 

 the full analysis of which even more diagrams might profit- 

 ably be employed. It is, in fact, highly desirable that the 

 charts be used freely and that, at every visit to a vantage point 

 of observation, a diagram should be plotted. It will scarcely 

 be necessary to state that the charts need only be marked in 

 the field and the final diagram filled in at leisure and after 

 mature consideration. It is recommended that the intercept 

 lines be drawn before the insertion of the letters and numbers. 

 These last may be done in red ink, if desired, which gives a 

 lesser interference with the figures, or the circles may be done 

 in red, which is very effective. The circles can easily be filled 

 with pen and ink — an operation which the employment of a 

 lens will facilitate and expedite. 



Very elegant diagrams for lantern projection may be made 

 by coloring, on the slide, those circles which would otherwise 

 be blackened. The diagram, in this case, is to be formed on 

 the card by the intercept lines and other markings but without 

 blackening the circles. This is then photographed, the slide 

 is made, and then the diagram circles are filled in with trans- 

 parent colors. Suitable tints are the following, beginning at 

 the upper radiant and proceeding clock-wise: violet, orange, 

 red, green, purple or black, yellow, blue, brown. 



It is, perhaps, inevitable that each living investigator would 

 have worked out a somewhat different diagrammatic method, 

 as personal experience is always vivid and necessarily affects 

 the perspective of a world-wide volcanism. It is only by trial 



