114 AKT. 3. — B. KOTÔ : 



The chief changes noticeable within tho range of temperature 

 from 800° to 1100° are those of augite, magnetite and glass of 

 the gronndmass in their relative proportions and also in their 

 development, corresponding to the varying consolidations of lava 

 during the effusive period. The effects of sudden quenching of the 

 test samples under icater do not appear to be strongly marked, 

 excepting the formation of glohullte in interstitial base. 



Very interesting features to be noted are the duration and 

 the degree of temperature to which the tests are subjected. The 

 longer in time and higher in the scale of temperature which the 

 tests have to undergo, the more perfectly both the augite and mag- 

 netite crystallize from the melts. This possibly depends on the 

 function of time of cooling and the relative proportion of volatile 

 constituents. 



In connection with the temperature of lava, a few words may 

 ÎPx^^^-i^"^'^^''^ be inserted on tlie formation of the ' block-lava ' and 



AND BrE4D- 



BomÏÏ ^li^' ' bread-crust bombs.' The diminution of pressure 



during the ascent of lava through the channel releases gaseous 

 contents, and the exothermal heat from the reaction of gases 

 counteracts the cooling by expansion and even can raise the tem- 

 perature to a certain degree. In coming to the surface the body 

 of the lava suddenly expands, thereby causing cooling, which is 

 accelerated by the cooler atmosphere. 



The manner of cooling from outside inward in such masses 

 must result in much mechanical deformation during the forward 

 movement. The projected masses turn to bread- crust bombs and 

 the flowing streams to discrete blocks — the ' Aa ' type of the 

 roughest and most ragged outline. 



secondaey Four months after the eruption the writer revisited 



Exhalation ^j^^ terminal cliff of the lava streams of the western 



