160 Part II. Chapter 2. 
uniformity are the direct heat received from the sun; the influence of the suc- 
cessive volume of aqueous vapor held in suspension in the atmosphere; the 
influence of the two great seas which wash the shores of the narrow belt of 
land connecting North and South America. The influence of the seas depends 
on their varying absolute temperatures and on the movements of the atmos- 
phere, as these, in a large measüre regulate the effect of the oceans in different 
months. The curves indicating the influence of the two oceans show that the 
Atlantic is much the more important. The northerly winds prevailing in the 
first four months of the year effectually prevent the Pacific, then relatively 
cold, from moderating the temperature at Panama. The joint influence of 
varying humidity and varying length of night is a more powerful factor in 
affecting the nearly unvarying annual temperature of the Isthmus than perhaps 
has been appreciated hitherto. 
Observed Air Temperature on the Isthmus '). 
Colon Gamboa | Alhajuela | Panama | La Boca Naos 
Month. 92 months. | 58 months. | 39 months. | 9 months. |41 months. | 70 months. en 
°C. n ge ee en nn cc 
January ... || 26.65 24.10 24.96 26.17 26.20 26.60 | 25.71 | 78.28 
February. . . 26.18 23.60 26.06 26.25 26.79 26.15 25.84 | 78.51 
March....| 26.47 24.15 26.55 26.62 27.25 26.33 | 26.23 | 7921 
Anl... 26.48 24.90 27.05 27.25 27.69 27.65 ‚| 26.34 | 80.38 
Mir... 26.73 26.85 25.55 27.07 27.01 27.90 | 26.85 | 80.33 
Jene... 26.73 27.70 26.21 26.69 27.23 28.85 27.23 | 81.01 
1 26.77 26.75 26.02 EN 26.69 28.31 26.91 | 180.44 
August. ... 26.23 26.60 26.20 2 26.10 28.00 | 26.63 | 79-93 
September 26.57 27.15 25.97 ei 26.46 27.94 | 26.82 80.28 
October... 26.18 26.55 25.46 26.45 25.84 27.45 26.32 79.38 
November. . 26.10 26.80 25.60 26.01 25.79 26.80 | 26.18 | 79.12 
December. . || 26.47 25.75 25.76 25.78 26.48 26.80 | 26.17 | 79H 
Means.... 26.43 25.91 25.95 26.48 26.63 27.40 26.48 79.66 
As is the case with the monthly means, the changes of temperature from 
hour to hour and from day to day are subject to much less variation on the 
Isthmus than in regions more remote from the equator. In connection with 
this study the fact that the rainfall on the Caribbean shore of South America 
is much less than in Panama, should be noted. During the period of ob- 
servations made there the average annual rainfall was, at Alhajuela, 103.8 inches; 
at La Boca, 74.5 inches; at Barbados, 39.6 inches: at Trinidad 56.5 inches; 
and at Curacao only 16.1 inches. It is evident ee an inspection of the 
accompanying consolidated table to February 1903 that an annual rainfall of 
about 140 inches may be expected on the Atlantic coast, about 93 inches in 
the interior, and about 60 inches near the shores of the Pacific. There is 4 
1) ABBOTT, General Hexry L.: Climatolo ther 
i HE f jy. Wea 
Review XXXI: 119. March 1903. gy of the Isthmus of Panama. Monthly 
