146 PHYSICAL GEOGEAPHY. 



In Table I. (1) is presented the monthly mean Temperatures 

 for the three observations taken, viz: 7 A. M., 2 P. M., and 

 9 P. M., for a period of thirty-one years, extending from 1839 

 to 1869, inclusive; together with the annual means for the 

 same period. At the bottom of the table may be found the 

 greatest and least of these means, with the mean for the 

 whole. 



An examination of the results here given, will show a great 

 range in many of these means of many observations, an ine- 

 quality far greater than might have been anticipated. 



In table I (2), the monthly and annual maximum (greatest) 

 and minimum (least), and mean temperatures are given. In 

 the column for the year the maximum and minimum are the 

 means of these results. An inspection of this table will show 

 that in this region — round about Iowa City — November and 

 March are essentially winter months, their mean temperatures 

 rising but a little above the freezing point, September, much 

 more than May, has a summer temperature ; the mean tem- 

 perature of the latter month being 69.06 degrees ; of the 

 former it is 63.37 degrees. The mean temperature of October 

 is 49.58 degrees, falling as low as 40.02 in 1863, and again in 

 1869 to 42.72. 



In order to show at a glance more plainly the variation in 

 the annual mean temperature, we present the same in the 

 form of a diagram (A), table I (3). The o in the left marginal 

 column, represents the mean annual temperature for the period 

 of thirty -one years, viz : 47.57 degrees — the range being three 

 below 44.18 and five below 52.14, or, 7.96 degrees in all, as 

 may readily be seen upon an examination of table I (2). 



Diagram B, table I (4), shows the extreme means of the 

 monthly temperatures ; the upper dotted line, the greatest 

 (maximum), the lower dotted line, the least (minimum), while 

 the full central curved line shows the annual monthly fluctua- 

 tions of temperature — all of which are deduced from the 

 results presented in table I (2). 



