Volcanic Eruptions 



iii 



with a moist layer above it, with the 

 result that the rocks along a part of the 

 line of contact would have their melting 

 point lowered, and would take up water 

 in combination, tending to increase in 

 bulk, and forming a mass having many 

 of the properties of ordinary lavas. The 

 swelling of the mass at a line of weak- 

 ness would tend to fracture the super- 

 incumbent rocks. The relief of press- 

 ure so obtained would set free large 

 quantities of the occluded gases and 

 vapors, and these would bring with 

 them rock materials in a solid and 

 molten state. A close analogy occurs 

 in the case of a bottle of soda water 

 when the cork is taken out, the sudden 

 liberation of the gas in solution driving 

 part of the water out of the bottle. 

 Thus volcanic lava, so far from being a 

 material distributed as a continuous 

 layer in all parts of the earth, is a spe- 

 cial product of regions which have just 

 undergone profound geological changes, 

 and the significance of this in relation 



to the geographical distribution of act- 

 ive volcanoes is very great. Again, it 

 becomes evident that the depths at 

 which centers of activity — i. e. , " pock- 

 ets" of swelling or expanding mate- 

 rial — are developed may vary consider- 

 ably, and we are able to account for the 

 fact that volcanoes near one another 

 may be quite independent, while others, 

 more distant, may act sympathetically. 

 Finally, lavas may originate in rocks of 

 widely different constitution — from crys- 

 talline rocks to the carboniferous clays 

 which produce anorthite lavas. The 

 indispensable factor, the tendency to 

 increase in volume, may of course be 

 supplied by other substances than water, 

 as, for example, by chlorides, like 

 masses of rock-salt, which would ex- 

 plain the emanations from exceptional 

 volcanoes, like those of Hawaii, where 

 the place of water vapor is taken by 

 hydrochloric acid or by sulphates or 

 combustible carbon compounds. 



GEOGRAPHIC NOTES 



THE FOUNDER OF THE SMITHSONIAN 

 INSTITUTION 



WORD has been received that James 

 Smithson, the founder of the 

 Smithsonian Institution, must be turned 

 out of his grave in Genoa, Italy, to make 

 room for a quarry. 



Smithson died at Genoa in 1829, and 

 was buried in a small and isolated British 

 cemetery on the heights of San Benigno. 

 The cemetery is under the care of the 

 British consul at Genoa, but the land 

 belongs to the Italian Government. 

 Near by is a quarry, from which the city 

 gets the stone for its works. Much 

 more stone is now needed for the exten- 

 sive harbor improvements which have 

 been begun, and hence all the graves in 

 the cemetery must be removed. 



Smithson left his entire estate of over 

 half a million dollars to "the United 

 States of America to found at Washing- 

 ton, under the name of the Smithsonian 

 Institution, an establishment for the in- 

 crease and diffusion of knowledge among 

 men." 



The princely legacy came as a surprise 

 to the United States. He had never vis- 

 ited this country, nor had he any Amer- 

 ican friends or, as far as we know, any 

 correspondents across the ocean. His 

 plan was unique and has given the 

 United States a scientific institution such 

 as no other nation in the world pos- 

 sesses. Today the institution which 

 bears Smithson's name, in addition to 

 the income of the Smithsonian fund 

 proper, which amounts to about $30,000 



