108 S. SEKIYA AND Y. KIKUCHI 



nearly one-half of the houses, with their inmates. Fi"'. 1 of PL XVII. 

 is a view taken from the outskirt of Inawashiro, at a distance of 

 nearly one kilometre from the mud field, showing the village of Miné 

 in front, and the avalanche (d) of rock and earth descending upon its 

 prey. Fig. 1 of PL XYIII. is another and nearer view of this mud- 

 field. 



The combined volume of these two great streams entirely 

 covered an area of 27 square miles, or 70 square kilometres, with a 

 solid sea of mud and rock, beneath which were buried all the features 

 of the landscape, together with people, cattle, and other living 

 things. The grey tint. on PL XV. marks the area thus devastated. 

 Velocity of the The descending matter must have moved with great velocity. 



descending mate- ., . . . ,,,.... 



j . by some survivors it was described as having reached their vicinity 



almost instantly after the eruption. From several calculations, made 

 by comparing the time of the explosion with the times at which the 

 streams of debris arrived at different points, we roughly estimated the 

 average speed to have been 77 kilometres or 48 miles per hour. On 

 its course the mud-stream must have swelled into «Teat waves, as in 

 a surging current. This is attested by eye-witnesses. The Avave- 

 like traces left on the sides of the hill (PL XX) show how the torrent 

 surged upwards when it met any obstacle either obliquely or at right 

 angles. In one case near Kawakami, the earth reached a height of 

 at least 40 metres above the general level on a hill facing 1 the direction 

 of flow and at other 40 metres places a spur of the hill which the 

 current struck obliquely caused an uprush of from 30 to 60 metres. 

 'The general appearance of the present surface is one of extraordinary 

 havoc and confusion, irregular lumps of earth being mixed up with 

 torn-off trunks and branches of trees, fragments of timber, and stray 

 boulders of huge size. In some places the matter has been largely 

 admixed with water, and is treacherous to walk on. 



