THE ERUPTION OF VESUVIUS IN APRIL, 1906. 229 



decrepitation of scoriaceoiis nuitter both coarse and fine. The acon- 

 midation of this material at the front of the flow is analogous to 

 similar material upon the basaltic flows of Auvergne and might 

 easily be taken for products of vertical ejections. 



The hna fields of 1906 at Boscotrecase are roughened with scoria- 

 ceous l)locks presenting strange forms. The surface is broken in 

 jjlaces by higher asperities due to the escape of gas or by great slabs 

 of lava broken by contraction and overturned by the continuous 

 progress of the subjacent lava, and there are also fissures more or less 

 profound. Among the surface blocks abound globular masses with 

 couipact crust and scoriaceous interior which have often been de- 

 scril)ed as bombs, whereas they are fragments of old lavas caught up 

 by the stream in the manner of the block above described. 



The lavas of April 6 to 8 from the fissures of Cognoli followed the 

 line of greatest slope. They filled ravines and minor depressions 

 and formed, where the topography permitted, small secondary cur- 

 rents Avhich in places reunited, leaving between them small oases 

 of verdure. Near the source the current is very distinct and is bor- 

 dered by black-covered moraines. The edges and front of the flow 

 near Boscotrecase are formed of talus, wdth a height locally of several 

 meters, ending abruptly in the midst of vineyards or among the 

 habitations of the people. 



The behavior of the lava in the cultivated and inhabited regions 

 has been varied. Roads lined with walls at right angles to the 

 greatest slope have been cut and the lava has in places gone some 

 meters in the transverse direction. "\Mien the route was parallel or 

 onl}' slightly oblique to the direction of the flow the lava has flowed 

 between the walls, and some of the streets of Boscotrecase are blocked 

 by a high wall of lava. The railway with its cuts and fills has fur- 

 nished obstacles or special facilities for the advance of the lava, 

 some of the cuts having been completely filled. At some of the fills 

 it has poured over the road and flowed in cascades down the farther 

 slope. In one case the lava flowed under a railway bridge and 

 stopped just in time to save it from serious damage. On cooling in 

 this railway cut it has formed a sort of highway with an even surface 

 some decimeters above the fields on either side. At 200 meters from 

 the front of this flow the railway reaches a level surface which has 

 been traversed by another ramification of the same flow. The two 

 rails at this point have suffered a symmetrical deviation, due to 

 expansion. Houses met various fates, according to their situation, 

 some being destroyed. Others were invaded by the lava, w'hich 

 found an entrance through doors and windows facing the mountain. 

 The lava was sufficiently fluid to fill the chambers and courts and to 

 mold itself there. It is hardly necessary to add that although the 



