546 



NA rURh 



[October 6, 1892 



of the rift had not sufficient power to eject large materials, 

 but lifted them up and kept them in continual movement, 

 reducing them to fine dust, which was easily carried out 

 by the vapour. No. 3, on the contrary, continually 

 ejected large lumps of lava, often shooting them a con- 

 siderable distance, whilst Nos. i and 2 exhibited inter- 

 mediate stages, quite confirming what has been said 

 above. 



Whilst we were there the eruption increased little by 

 little. The ground commenced to vibrate,and at 3.47 p.m.we 



Fig. ^. — Taken by Sig. Modo on July i8, 1892, at 300 m. to the northwest 

 of the craters, (i and 2) craters No. i and 2. (a) Monte Nero, {d) 

 Craters to the west which were in activity only on July 9. 



felt a strong earthquake shock, followed by other frequent 

 oscillations of the ground of less intensity but often very 

 perceptible. In this new period of great activity general 

 to all the craters the phenomena exhibited by No. 2 

 were worthy of remark. It no longer ejected dust, butpieces 

 of hot lava with stronger explosions, which were more 

 frequent but of shorter duration. Between one explosion 

 and another there was slow evolution of white vapour, 

 similar to that which rises from the fire-mouths and 



Fig. 5.— Taken by Prof. Riccu on July 20, west of.ihe craters, (i, 2,3). 

 craters No. i, 2, and -i. 



surface of the running lava. This floated above the 

 crater, slightly disturbed by the wind, and when an 

 explosion occurred it assumed a curious vibratory move- 

 ment, rising a little, and then rapidly descending ; then 

 imrnediatel y was seen the first jet of solid materials, which, 

 in its vertiginous upward course by vortex movement, 

 sucked in the air over the crater edge, and the white 

 vapours were drawn down, so looking as if they were 

 being reabsorbed. This phenomenon, which attracted 



our attention when I was with you on Stromboli and the 

 members of the Geologists Association,^ would show 

 that within crater No. 2 there is pasty lava, which is- 

 pushed up by the vapour in it ; then the magma swells, 

 up, bursts, and the lava falls.- 



In this parasitic crater of Etna, however, the pheno- 

 mena were on a much larger scale, as also were the smoke 

 vortex rings which we looked down upon when we were 

 together at Stromboli. Likewise the explosions were far 

 louder, reverberating as a low-pitched roar by the echo of 



Fig. 6.— Taken by Prof. Ricct) on July>o,'to-the 

 No. I, 2, and 3. (a) Monte Nero. 



r.orth-west of the crater 



the valleys, and they were audible in all the Etnean region, 

 at Catania, Acireale, Giarre, and farther still for some 

 dozens of kilometres from the craters. The air-shocks that 

 accompanied these reports were very interesting. They 

 represented a large undulation of the air, spreading 

 with great velocity, reaching great distances, and con- 

 temporareous with the audible vibrations.^ While there, 

 we felt the blow on our bodies, and especially our 

 chests and in the ears ; at the Casa del Bosco we de- 

 tected the shock against the walls, which trembled, and 



NO. 1197, VOL. 46] 



Fig. 7.— Taken by G. Pla'ania from the north-north-east of the craters, July 

 30, 1891. (i) Crater No. i. (c) Craters which were in activity only on- 

 July 9. The craters No. 2, 3, and 4 are hidden behind crater No. 1. )._ 



farther off at Catania and Acireale we heard the 

 rattling of the windows and doors, which, strongly shaken, 



I G. Platania "Stromboli e Vulcano, nel Settembre del 1889. Riposto 

 18&9." This phenomenon I have ohtn obser\ed at \esuvius, and 1 quite 

 agree with Signer Plaisnia as to its cause, as I have been able to look into 

 the crater and watch the whole process. — Johnston-Lavis. ... 



^ Ihe lava in this case is very hke the boiling up of a viscous liquid in a 

 long test-tube, — Johnstcn-Lavis. 



3 I have some doubts about the two mechanical disturbances travelhiig 

 exactly at the same rate. When blasts are fired in a loijg tunnel the aii- 

 stroke is felt before the sound. Johnston-Lavis. 



