THE ERUPTION OF BAXDAI-SAX. 143 



eruption, which took place on the south -eastern flank of Fuji-yama 

 in the 4th year of Höyei (1707 A.D.). By this outburst a great 

 chasm very similar in its character to that of Bandai, was opened 

 on the mountain side. It is an explosion-crater not inferior in 

 magnitude to the latter. Höyei-zan is really a prominence on the 

 outer rim of this great chasm. It has, however, hitherto been 

 regarded as an example of a 'parasitic cone.' It is to be observed 

 that, in case of the Fuji explosion, there were produced numerous vol- 

 canic bombs, which are now found scattered all around the crater, 

 showing that there was ascent of lava. Another striking phenomenon 

 is the presence of a magnificent series of numerous vertical dykes 

 which traverse the side- wall of the crater. On the other hand there 

 may be seen on the perpendicular walls of the newly opened crater of 

 Bandai, bands of volcanic strata exposed, consisting of an alternation 

 of old lava-streams, and of agglomerates of fragmentary materials, a 

 singular feature of these strata being the absence of any noteworthv 

 dykes passing through them. This fact would show that since the 

 formation of the Bandai group, the mountain has been very little at- 

 tacked by the intrusion of molten magma from the interior. 



Again, as we have already seen, among the products of the late 

 eruption there is no lava. There are, however, among the debris, 

 especially near to the spot where the steam-jets are issuing within 

 the crater, some greenish coloured rock-specimens with disseminated 

 patches of iron-pyrites, and a white coloured sintery rock having 

 a bleached appearance, almost wholly consisting of silica as shown 

 by the analysis given in the sequel. These materials indicate the 

 action of fumaroles and hot springs in altering the rocks in the 

 interior of the volcano, and in depositing mineral matter while per- 

 colating through the crevices. Among the debris that ran down 

 to the north, are often found porous or scoriaceous rocks of a reddish 



