Ixxxvi. president's address. 



they arrived at the conclusion that the mechanism of the hot 

 blast and the source of power which propelled it, together with 

 the strange phenomenon of the descent of a black cloud which 

 succeeded it, at Mont Pelee, was entirely due to Gravity as in the 

 case of an ordinary avalanche. To use their own language, 

 " The lava which rises in the chimney of the volcano is charged 

 with steam and gases which explode as usual, but some of the 

 explosions have only just sufificient force to blow the mass to 

 atoms and lift the greater part of it over the lips of the crater 

 without distributing the whole widely in the air. The mixture 

 of solid particles and incandescent gas behaves like a heavy 

 liquid, and before these particles have time to subside, the whole 

 rolls down the side of the mountain under the influence of 

 ' gravity,' and consequently gathers speed and momentum as it 

 goes." The discovery is a valuable result of the patient observa- 

 tion shown by these gentlemen, who, carrying their lives in their 

 hands, started, as Dr. Anderson tells us, with the comfortable 

 assurance of their friends that they would certainly be killed, but 

 that afterwards in the next world it would be a very great satis- 

 faction to them to think that they had lost their lives in the cause 

 of science. Of the close connection between earthquakes and 

 volcanic eruptions, geologists in recent years seem to entertain 

 little doubt, and we cannot therefore be astonished that the past 

 year has been remarkably prolific of every form of subterranean 

 disturbance. Professor IMilne has pointed out that 50 world- 

 shaking earthquakes occur every year, and that most of these 

 have their origin near the steepest flexures on the face of the 

 earth. In many cases they are submarine and originate in 

 furrows, which become deepened, whilst the neighbouring ridges 

 undergo elevation. Turning to matters nearer home, the 

 discovery and continued abundant supply of natural gas at 

 Heathfield, in Sussex, having its origin in the strata of Kim- 

 meridge clay, may, and probably will, have an important bearing 

 upon the industries of Dorset. Some weeks ago I had the 

 privilege of visiting that part of Sussex in which these discoveries 

 have been made, and I was very much struck by the enormous 



