MODIFICATIONS OF TEMPERATURE. 21 



"One thing more than any other that dominates the physical and 

 mental being is climate. The delights of atmospheric conditions, where 

 neither heat nor cold obtain, affect most favorably the physical and 

 mental condition. The body revels in a sense of painless enjoyment, 

 and the mind, freed from the depressing influence of an uncomfortable 

 body, has the whole realm of existence for a pleasure ground." 



By her arid semi-tropical endowment California escapes the trying 

 conditions of both the tropics ,and the frigids. This is a fact to which 

 the many who have sought California homes from all parts of the 

 world continually bear witness. 



GARDEN MODIFICATIONS OF CLIMATE. 



It may be readily inferred that in climates naturally so kind to 

 plant growth, modification, for cultural purposes could be slight and 

 easily affected. This is. absolutely true as to the operations of the 

 working amateur, for he has such a breadth of activity with plants 

 needing no artificial heat that he is but seldom prompted to provide it 

 except in the simple ways outlined in Chapters IX and X. Of course 

 the commercial grower and the occasional amateur, whose taste re- 

 quires orchids and the like must have temperatures under complete 

 control and production just as the same interests are served in other 

 climates, except that the result is far more easily and cheaply secured. 

 But with that we have nothing to do in this book. Our suggestions 

 are restricted to conservation of natural heat, either : by direct use of 

 trapped sunshine or by indirect use of sun-heat through checking loss 

 of it by radiation from the earth. But even these elementary affairs 

 have been so effectively developed in commercial fruit growing of 

 California that they present themselves with a wealth of detail which 

 cannot be fully presented in this connection. * For ordinary garden 

 use these suggestions may be helpful: 



Higher heat during day time and escape from a freezing tempera- 

 ture at night, may often be secured by planting windbreaks of trees 

 in hedge form or as shelter belts traversing the direction from which 

 cold winds may be expected to blow in. Glass screens or lath fences 

 serve the same purpose for small areas. The height should be pro- 

 portional to the area to be protected. A hedge or screen ten feet high 

 may amply protect a small garden, belts of tall trees will be needed 

 for an area of several acres. 



A few plants may be saved from frost by spreading over them a 

 cover of cloth, paper, carpet, rush-mats, lath frames, etc. These act 

 by holding ground heat from radiation, and will be effective against 

 several degrees of frost continuing for hours. 



* Discussion of achievements in this line are found in publications by the U. S. 

 Weather Bureau and by the California Experiment Station. 



