EVAPORATION AT PALERMO. 



461 



that is to say, least in winter, greatest iu summer, nearly equal in 

 spring- and autumn, being more restricted in the latter season, lor 

 reasons which will be easily perceived from the following table : 



For a first approximation, therefore, we may calculate the mean daily, 

 monthly, and annual evaporation, as well as that for the seasons, by 

 employing the coefQcient only of the temperature, t = 0.20G75. Thus, 

 taking the mean monthly temperature derived from the observations 

 of seventy-six years, we form the following table : 



Months. 



Mean tem- 

 perature 



Daily evapora- 

 tion as cal- 

 culated. 



Monthly evapo- 

 ration as cal- 

 culated. 



Mean quantity 

 of rain as ob- 

 served. 



January... 

 February . . 



JIarch 



April 



May 



Juno 



July 



August 



September. 

 October . . . 

 November . 

 December . 



-f 10. OS 

 11.15 

 12. 42 



14.86 

 18. 59 

 22. 34 

 25. 04 

 25. 22 

 22.98 

 19. 68 

 15. 57 

 12. 30 



MilUvictej's. 

 2. 270 

 2.305 



2. 567 



3. 072 



3. 843 

 4.619 

 5,176 

 5.214 

 4. 751 



4. 068 

 3. 218 

 2. 544 



Millimeters. 



70. 37 



65. 12 



79.59 



92.16 



119. 13 



138. 57 



loO. 46 



161. 64 



142. 53 



126. 11 



96. 54 



78.86 



Millimeters. 

 71.74 

 63. 55 

 72. 69 

 42. 65 

 26.60 

 17. 21 

 5. 80 

 9.11 

 51.88 

 71.65 

 72. 2S 

 83.80 



Hence, as regards seasons, the evaporation results as follows : 



Millimeters. 



Winter 214.35 



Spring 290.87 



Summer 4G0.G7 



Autumn 305.18 



Annual mean 1331.07 



In regard to the water which fell, it will be seen that in the months of 

 January, February, March, and December, the evaxioration urns nearly 

 equal ^ and that the annual evaporation ivas equal to ticice and one-fourth 

 the qiiantity of rain. 



The Gaspabin evaporator. — With this atmometer the inconveni- 

 ence constantlj^ presents itself that, on days of rain, the indications 

 Xjoint to erroneous results, through the impossibility of applying the 



