SECRETARY'S REPORT. 77 



variety may be successfully grown, and in the St. Lawrence 

 valley, it is the 47th parallel. The most important exception 

 is a narrow line of the Pacific coast, and to this there is a gen- 

 eral addition of some of the most considerably elevated localities 

 in mountainous portions, — say the mountainous elevations of 

 Maine, New Hampshire, Vermont, Wisconsin, Minnesota, and 

 northern New York, east of the Rocky Mountains. 



The maximum capacity of the production of Indian corn is 

 nearer its northern than its southern limit, and indeed even in 

 those States where it may sometimes be cut off by extremes of 

 temperature, say Wisconsin, northern Illinois, Michigan, central 

 New York, and southern New England. This is doubted by 

 some, as large yields have been made at the south. There are, 

 however, great irregularities in the climates within these limits 

 and they correspond in the produce of Indian corn. The tem- 

 perature extremes sometimes seem to sweep over large tracts of 

 country. In eastern Oregon, valley of the Great Salt Lake, and 

 the upper (but not the lower) valleys of the Grand and Green 

 Rivers, (Colorado of California,) and Rio Grande, it is injured 

 by the daily changes of temperature, though the mean is high 

 enough. 



On the coast of the Pacific, west of the coast range moun- 

 tains, from San Diego to Puget's Sound, nowhere does any 

 month attain a mean temperature of 65°, or permit the ripening 

 of Indian corn. From the sea to that range it is less than 60° 

 mean in July, and where the range is low, this low mean 

 extends inland as far as the principal mountain ranges ; but 

 the San Joaquin and the Sacramento valleys are nearly all that 

 have a sufficiently high and equable summer temperature in the 

 middle of the day, which corn indispensably demands for ripen- 

 ing and will not do with any less, unhindered by the daily 

 changes. The cool mornings, evenings, and nights of the east 

 do not affect it, if the midday be very light and beyond the 

 temperature of 65° during its growing and ripening months. 

 In this, corn is not elastic or adaptive. 



The northern line of cultivation of Indian corn, then, starting 

 in 64° to 67° of west longitude from Greenwich, at the Bay of 

 Fundy and the valleys of New Brunswick, at the 46th parallel 

 of north latitude, and going west, falls to less than 45° in high- 

 lands of Maine, in New Hampshire to 44°, then rises abruptly to 



