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Fourth, the Nimbus or storm clouds are any from 

 which rain falls. By some they are not regarded as a 

 distinct form of cloud. These primary classes form 

 various other shapes and figures which are called sec- 

 ondary clouds, but are only a combination of the for- 

 mer classes. 



Natural changes are many and are taking place over 

 all parts of the world. Rivers are doing a great deal 

 in this line, as they widen and deepen the channels 

 through which they flow, and in many cases make new 

 ones. In this way the coasts of continents are often 

 changed. The ocean takes a very active part in this 

 work, as we notice islands disappearing in some places 

 and appearing in others. Portions of the coasts 

 are constantly changing some rising and others sinking 

 thus proving the existence of universal action among 

 the elements. Earthquakes and volcanoes also produce 

 perceptive changes in the surrounding country. Coral 

 insects also form new land where none before existed. 



The general color of the ocean is deep blue while in 

 some places it is a green or red cast, owing to the pres- 

 ence of minute organisms. Waters are divided into 

 various classes, according to their composition and 

 qualities. Calcareous waters or springs are those which 

 contain lime. Solicious, or those containing silicon, 

 come under the head of Geysers. Sulphurous waters 

 or those containing metalic sulphides or sulphates; 

 Chabylsate or those containing iron; and Ascidulous 

 waters or those containing large quantities of carbonic 

 acid, also brines like the oceans and seas. 



Springs are likewise divided into various classes. 

 There are hot springs or geysers which send large quan- 



