468 Royal Institution. 
soils, as well as to their formation. Finely-divided matter 
is carried by rivers from the higher districts to the low 
countries, and alluvial lands are usually extremely fertile. 
The quantity of habitable surface is constantly. increased 
by these operations ; precipitous cliffs are gradually. made 
gentle slopes ; lakes are filled up; and islands are formed 
at the mouths of great rivers. 
In these series of changes, connected with the beauty and 
fertility of the surface of the globe, small quantities of so- 
lid matter are carried into the sea; but this) seems fully 
compensated for by the effects of vegetation in absorbing 
matter from the atmosphere, by the production of coral 
rocks and islands in the ocean, and by the operation of 
volcanic fires. ts 
By wise and beautiful laws, the equilibrium. of things ‘is 
constant. Life is preserved by operations which “appear 
destructive; order and harmony arise from. what ‘at’ first 
view seems derangement and confusion. The 'pérfection 
of the work is perceived the more it is studiedy’ and it de- 
clares, in distinct language, the power and wisdom of the 
Author, DA BLAC 
_ Lecture VI.—In pursuing the subject ‘of the’changes 
taking place in the solid parts of the surface of the-globe, 
Mr. Davy devoted the principal part of this lecture to the 
consideration of the causes and effects of volcanos.» 
To persons who inhabit countries not liable to these ph- 
nomena, they appear rather as accidents. than’ as ‘essential 
events in the order of things : but their/extenty their con- 
staney, and their ultimate tendency, leadito a very different 
conclusion, and show that they are even necessaky’and use- 
tul in the great series of the phenomenaiofnature: — 
Volcanos have been active in all times,‘ and! in all quar- 
ters of the globe. A considerable part of Italy, of Sicily, 
and of the South of France, is volcanic-—The Cordilleras 
of South America, the highest mouhtains of the world, 
abound in these fires ; and in Iceland, and the Asiatic Ar- 
chipelagos, their effects are constant. J 
The striking circumstances in all the great volcanic 
eruptions are, said Mr, Davy, great productions’ of elastic 
matter, by which the ground is shaken and rent asunder, , 
and earthquakes produced, and the pouring forth of a 
fused and ignited mass consisting of the earths in intimate 
combination. 
Some persons have attempted to account for volcanic 
fires by supposing a central fire in the interior of the globe : 
but this notion, says Mr. Davy, cannot well be supported ; 
for . 
