AND THE WEST INDIAN ERUPTIONS OF 1902. 



217 



It was this dust, or fine ash, of which samples have been 

 brought to this country from the islands of Barbados, where it 

 fell at a distance of 100 miles from its place of discbarge. As 

 will be seen from the specimens, this volcanic ash is a fine grey 

 powder, tlie largest particles being less than -J^ of an inch. 

 Under the microscope it is found to consist of crystals of 

 plagioclase felspar, hypersthene, augite, and magnetite with a 

 small amount of volcanic glass. An analysis by Dr. Pollard 

 gave the following result* : — 



Silica 



... o2-81 



Oxide of titanium 



•95 



Alumina ... 



... 18-79 



Peroxide of iron ... 



... 3-28 



Protoxide of iron ... 



4-58 



Oxide of manganese 



•28 



Oxide of cobalt and nickel 



•07 



Lime 



0-58 



Magnesia ... 



... o^ll) 



Potash 



•GO 



Soda 



... 3^2:; 



Phosphoric acid ... 



•15 



Sulphuric acid 



•33 



Chlorine ... 



•u 



Water 



O / 





100^35 



It is an interesting fact that the ash from St. Vincent was 

 carried to Barbados by an upper current of air moving in the 

 contrary direction to the surface wind which was the ordinary 

 " trade wind " of the region, from east to west, the island of 

 Barbados being due east from St. Vincent. 



Apart from the extraordinary incandescent avalanches of the 

 ^Martinique volcano, the West Indian eruptions of 1902 have 

 not exhibited phenomena other than normal. Their magnitude 

 has been often exceeded, and in our own times the Krakatoa 

 eruption of 1883 was a much greater one, with much more 

 topographical derangement, and equally great destruction of 

 human life. 



^ Nature, June 5th, 1902 



