BOTANY OF LA SALLE COUNTY. 13 



the mean of the six warmer months and that of the 

 six colder months to obtain our mean, we may have for 

 the first 80 deg. and for the latter 20 deg-., for 80 

 plus 20 divided by 2 equals 50; or we may have 70 plus 

 30 divided by 2 equals 50; or 60 plus 40 divided by 2 

 equals 50; or 50 plus 50 divided bv 2 equals 50. Of 

 these the first would indicate a warm summer and a 

 cold winter, the last a very equable climate, or very 

 little if any difference between summer and winter. 

 Such comparisons are therefore the sheerest humbug-, 

 making- things appear alike which have no possible re- 

 semblance and conveying- totally false ideas. Besides 

 they neglect other very important elements of climate 

 moisture and its distribution through the year. 



If we take the monthly . means of temperature for 

 the year we g-et a better idea of the climate of a region, 

 but these will be to no little extent modified by local 

 causes and must be reg-arded as only approximately 

 correct for places even a short distance from the 

 place of observation. Especially is this true of the 

 table of temperature given below, for Ottawa is 

 but 484 feet above the Gulf of Mexico, while some 

 points in the northwest corner of the county reach an 

 altitude of over 800 feet, and many points are 700 to 

 750 feet above sea-level, 



We are able to check the Ottawa observations, made 

 for the United States Weather Bureau, by a series 

 kept at Farm Ridg-e, ten miles southwest of Ottawa 

 on a hig-h ridg-e, not less than 700 ft. above sea-level, 

 but with a less accurate thermometer and with lesc* 

 attention to the time of observation, as they were 

 made with no intention of publishing- them. 



In the following table we g-ive the hig-hest and low- 

 est temperature for ech month, instead of the mean 

 temperature. 



