THE SCOPE OF NATURE-STUDY 25 



h) The seasonal : those which accompany the changes of tem- 

 perature and other modifying cHmatic influences. 



The observations under this division should take several 

 directions : 



(i) Toward a determination of the amount of sunshine. With 

 the younger pupils, the variation in proportion to the day's length 

 and to the amount of cloudiness can be understood. With older 

 pupils, the relative values of sunshine, also, determined by the vary- 

 ing slant, can be calculated from measurements easily made. 



(2) Toward a determination of the temperature of the air, of the 

 soil at different depths, and of bodies of water. 



(3) Toward a determination of the amount of moisture in the 

 soil at different depths and in the air. 



(4) Toward a determination of the amount of rainfall, and the 

 distribution of rainy days through the year. 



(5) Toward a determination of the amount of water, ash, and 

 other constituents in plants at different periods of growth. 



(6) Toward a study of all the habits of plants and animals — 

 germination, growth, maturity, nesting, feeding, migration, etc. — 

 that are associated with the season and conditioned by it. The pres- 

 entation need not be in accord with any fixed order ; the topics 

 indicate merely the general observations that should be made. 



c) Those operations resting upon profound causes, which, 

 gradual and subtle, effect radical and permanent changes. Thus 

 the slow drainage of a marsh (it may be for the purpose of agri- 

 culture), the denudation of the country of its timber, the encroach- 

 ment of the water upon the shore or coast line, the shifting of the 

 sand-ridges by the wind, the breaking of the shelving rocks in the 

 cliff", are all changes which almost imperceptibly, but profoundly, 

 affect the balance of parts in the landscape. These changes differ 

 from those first named in being more gradual, and from those 

 mentioned second, in being irregular. Whatever there may be of 

 recurrence is at intervals that seem to be variable. 



4. The study of landscape details, therefore, means the follozving 

 of each minor unity, through each of these series of aspects as the 

 changes occur, zvith due regard to the relations of the various 

 aspects to each other. — For example, a tree presents certain phases 

 of life which are due to the daily and hourly shifting influences of 

 sun and shower, of light and darkness, etc. ; these phases are 



