2a SMITHSONIAN I^llSCKI.I.ANKlHiS COLLECTIONS VOL. 69 



is accompanied hv comparatively li.ulU, but not iuficnucnt, precipita- 

 tion aloiit: most i^arts of the Atlantic sIodc. At this season rather 

 lijjht cloml formations discharge their moistnrc alonj;^ the northern 

 side of the Isllimns. the rainf.ill of the C(Kist dependint;- in a measure 

 on the heij^Iit and pro\iinit\ ol \]\c moniitains. At the his/her eleva- 

 tions foj^s are very prevalent, and are often so dense that one's 

 vision penetrates only a few tecl, and the ditnly li^^hted forest be- 

 comes still darker as the cloud mass settles down ; a fine spray drifts 

 throutih the trees and soon the leaves are dripping- steadily. The 

 Pacil'ic coast, in marked contrast, has a true dry season, during 

 which little or no vain falls, nuring- the wet season, beginning 

 usually alunit the latter part of May and ending about the lirst of 

 December, southerly winds become dominaiit anil rains are more 

 general thrt)Ughout the Isthmus. Al (lu> Tanal Zone, which is a 

 cross-section of the Istlnnus about 50 miles in extent, the amuial 

 rainfall on the Atlantic coast is about double that on the Tacilic coast. 

 Ofhcial records for mmk) show a total rainfall of <)3.o() inches at 

 r>alboa, and 1S3.41 inches at Cristobal; but the average for 13 years 

 at the former slatioji is 71.67. and for 40 years at the latter station 

 130.03. This relative luunidily of the two sides probably obtains as 

 far west as the Costa Rican frontier, but in eastern Panama the 

 dilYerence is less marked. In nnich of the Darien region the total 

 rainfall is increased to an annual precipitation of perhaps more than 

 200 inches ' which renders this area one of the wettest in America. 



Excepting at the Canal /one ami limited areas in western Panama 

 the republic is sparsely populated by man; clearings are few, and 

 aside from the ratlur extensive, open, grassy savannas near the 

 Facitic coast and smaller grass areas in the Chagres N'alley, the 

 Isthmus is a practically unbroken exjxmse of forest. Under the 

 stinnilating intluence of freiiuently recurring' showers and con- 

 tinuously nuMst conditions throughout the year, the Atlantic water- 

 shed maintains a much more exuberant growth of vegetation than 

 the Pacific watershed, where long periods of drought check vegetative 

 vigor. At the height of the ilry season these climatic diiTerences 

 are manifested in the contrasting asjuvt of the forests on the two 

 slopes. While the trees oi the .Atlantic forest are clothed with 

 brilliant evergreen foliage, those of the Pacific forest, truly deciiluous 

 for the most part, present bare stems, and the landscape has an 



* During the construction of the raiuiiua Catial -0"--^ inches was recorded 

 in a single year, and 58 inches in a sinjjlc month at Porto Bello, Panama ; the 

 annual avora.ijc. however, was 17*^67 during throe years of rocoril. 



