AND THE WEST INDIAN ERUPTIONS OF 1902. 213 



conspicuously seen in this country. The eruption was heard 

 3,000 miles away, it produced an ocean-wave that caused 

 great devastation, and an atmospheric wave that affected the 

 barometer of Greenwich Observatory. 



In the same region, the eruption of Papandayung, in the 

 island of Java, in 1772, was of such terrific violence that a 

 depression fifteen miles by six was formed, the whole mass 

 previously occupying that area having been blown away. 



A purely explosive eruption on a small scale was that of 

 Monte iSTuovo, near Baiic on the shore of the Bay of Naples, 

 in 1538, by which a cratered hill was formed by an ejection of 

 fragmentary material from a newly opened vent, from which 

 no lava has ever flowed. 



The eruptions that are both emissive and explosive are the 

 most usual, and they exhibit the most varied phenomena, since 

 in these the characteristics of the non-explosive are added to 

 those of explosive eruptions. The modern eruptions of 

 Vesuvius and the eruptions of Etna and Hecla, are good 

 examples of this class. Premonitions are commonly given by 

 earth-tremors and subterranean rumbling noises occurring 

 immediately preceding, or very shortly before, the outbreak ; 

 and very delicate and elaborate instruments, such as the late 

 Professor Palmieri's seismograph at the Eoyal Observatory on 

 Vesuvius, are sometimes employed for the detection and 

 registration of these warning symptoms. 



According to their character and relative violence these 

 eruptions may be termed strombolean," when there is slight 

 hut, during a prolonged period of time, continuous eruptive 

 energy ; moderate or normal, when the eruption is not a very 

 great one ; and " paroxysmal," when it is of mucli more than 

 usual violence. 



A flow of lava may either precede, accompany, or follow, 

 the ejection of scoricne and ashes, and may flow over a lip of 

 the crater or through a tunnel in the crater-wall, or it may be 

 emitted from an opening or openings on the slopes of the 

 volcano. Eruptive energy may also be manifested at more 

 than one point at the same time on the same volcano. Thus 

 violent explosive ejections of scoriae and ashes may be going 

 on from the summit crater while lava is being quietly emitted 

 from one or several orifices far below. 



The explosive ejections, accompanied by a rushing roar, 

 occur with very small intervals of time between, but they are 

 usually distinctly separated when the eruption is not of great 

 violence. The fine volcanic ash, much of it the result of the 



