fiii CONTENTS. 



Chapter III. — Effects of Forests on Marshes, - - 73 



Section I. — On the Brying-up of Marshes on the Growth of 



Trees, - - - - - - 73 



It is stated that what is evaporated through the stomates of the 

 leaves is derived from the ground (p. 73). and Ihit the quantity 

 often exceeds many times that of the rainfall (p. 74); that to a great 

 extent what the atmosphere thus gains the earh loses (p 79); and 

 an illustration of the effect in drying up wet ground is given (p. 80). 



Section II. — On the occcasional appearance of 3farshes on the 



destruction of Forests, - - - - - 81 



Cases of the appearance of marshes on the destruction of forests are 

 cited, which are attributed to the interruption of the withdrawal 

 of excess of moisture from the soil by the trees (p. 81). 



Section III. — On the occasional Destruction of Forests by the 



Creation of Marshes, - - - - - 83 



The destruction of forests by marshes is attributed to the damming- up 

 of water outle's at a lower level (p. H3), and illustrative cases are 

 given from Russia (p. 83), Canada (p. 85), and the United States 

 of America (p. 88). 



Section IV. — On the Desiccating Effects produced on Marshes 



hy Forests in prolonged periods, - - - 90 



The gradual conversion of marshes into habitable and arable land is 

 discussed (p. 90), and Ireland and Denmark are referred to in 

 illustration (p. 91). 



Chapter IV. — On the Effects of Forests on the Moisture of a 



wide expanse of Country, - - - - 93 



Section I. — Cases in which the extensive destruction of Forests 

 does not appear to have perceptibly affected the quantity of 

 the Rainfall over a wide expanse of Country, - - 94 



The difference between moisture and rainfall is pointed out (p. 94) ; 

 and illustrations of little eff ct having been produced on the quantity 

 of rain falling over a wide expanse of country having been produced 

 by an extensive destruction of forests are given from France (p. 95), 

 and from the United States of North America (p. 98). 



Section II. — Cases in which the extensive destruction of Forests 

 appears to have been followed by a marked desiccation of 

 Land and aridity of Climate, - - - 99 



It is stated that the extensive destruction of grass and herbage and 

 trees in South Africa has been followed by drought (p 104); and 

 there are cited statements in regard to corresponding observations 



