DRAINAGE AND CLIMATE 



213 



TABLE XXIII 



MEAN TEMPERATURE FOR THE MONTHS OF DECEMBER, JANUARY, 

 AND FEBRUARY 



285. Changes in frost dates. It is said by old resi- 

 dents of southern and central Michigan and other 

 originally forested parts of our country, that with the 

 cutting away of the timber and draining of the lands of 

 these regions, the periods between late spring and early 

 fall frosts have been greatly lengthened, so that certain 

 crops can now be grown that could not be grown in pioneer 

 days. Records are not easily found to verify these claims. 

 The claims, however, do not seem unreasonable. Very 

 definite relation exists between air drainage and the 

 occurrence of frosts. The practical orchard ist recognizes 

 the great importance of air drainage in the selection of 

 an orchard site. After the first light frost, the affected 

 areas are found to occupy the depressions and ravines of 

 the field, and are as clearly defined as would be the shores 



1 Walter H. F. Grau, Harper's Weekly, Vol. 152, No. 2713, p. 8. 



Data procured in part from "reliable private records," and 

 from those of voluntary observers cooperating with the Smith- 

 sonian Institution. 



