ISOTHERMAL CHARTS. 



The following charts have been prepared for this report by the Sig- 

 nal Of&ce of the U. S. Army. I desire to thank General Hazen and his 

 assistants for the valuable services they have so freely given. 



First are given charts of the mean temperature of the several months 

 from March to l^ovember. Isotherms, which promise to be of peculiar 

 interest in the sorghum industry, are marked in heavier lines. The 

 careful student of the sugar industry will be struck with the irregularity 

 of these lines, and especially as they approach the Pacific coast. 



The great deflection southward, caused by the Eastern mountain 

 ranges, will also be carefully noted. 



Following the charts for the several months is found one which gives 

 the mean summer temperature for the three months of June, July, and 

 August. By almost unanimous consent, those who are interested in 

 sorghum as a sugar-producing plant have assigned the isotherm of 70° 

 F. for the summer as the northern limit of successful sorghum culture, 

 while the growers of the sugar-beet look for their greatest success north 

 of that line. The track of this line, therefore, across the continent will 

 be traced with interest. It will be seen that the great corn-producing 

 regions of the Northwest lie almost wholly south of this line. Its direc- 

 tion from West Virginia due north almost to Buffalo is a very striking 

 peculiarity of its course. In most seasons sorghum in some of its varie- 

 ties can be grown to maturity south of this isotherm. 



While the isotherm of 70^ for the summer months is of greatest in- 

 terest to sorghum growers, the manufacturer will devote more atten- 

 tion to the lines of 65^ for September and 55° for October. The season 

 for manufacture must include these two months, and perhaps also ^To- 

 vember. The most important line on the November chart is that of IQo. 



I should have added one more chart, viz, one showing the mean posi- 

 tion of a line constructed from the isotherms of 65 ^ for September, 55° 

 for October, and 40^ for November. Such a mean line, in my opinion, 

 would mark out very nearly the northern limit of successful manufacture 

 of sugar from sorghum. Any one interested can get a good idea of the 

 position of this line by studying together the three charts above men- 

 tioned. 



No attempt has been made in these charts to introduce the question 

 of rainfall. East of Kansas this is not one of great importance. Over 

 limited areas of the corn-producing region the crops are often injured 



