222 METEOROLOGY. 



leaf thatcbed roof, resting upon six isolated posts,) near to which a 

 tiger was said to have his range. Towards evening torrents of rain 

 poured down ; but the night was still and undisturbed, except by the 

 rushing mountain-stream at some distance oif, which appeared to the 

 watchful ear like the hollow rustling of a forest in a gale of wind. 

 One solitary bird near by made the spot still more melancholy by 

 its mournful notes, which it sent forth from time to time throughout 

 the night, unanswered by anything living. 



These damp and shady primeval forests, especially when fronting 

 the sea, ar^ also to be noted for the great amount of ferns, with regard 

 to species as well as to individuals. This beautiful class of plants, of 

 which I have already collected 489 species within a comparatively 

 small part of the country, loves moisture, shade, and stagnoMt air, and 

 rarely ever succeeds in a climate or region which lacks these three 

 great necessary conditions. With regard to number of individuals, 

 the different heights show no marked effect. I found them in masses 

 equally dense at 1,50U and 6,500 feet elevation ; and I have descended 

 and ascended the flanks of the coast-chain in five different regions. 



The only difference we see is the change of species in different 

 heights, and even here we find many species to extend over a great 

 area of different elevation ; but most species are rather of a local habit. 



We can, therefore, from the amount of ferns which occurs in any 

 given place, not very well deduce the mean temperature of that place, 

 as is sometimes done in geology, in conjectures about the temperature 

 of the earth's surface at the time of deposition of the coal fields, unless 

 we know what temperature belongs to the luxuriant growth of that 

 very species which we wish to draw conclusions from. The yearly 

 mean temperature of the fern region may vary from 56° to 80° F^ 



CoLONiA TovAR, VENEZUELA, January 10, 1858. 



Dear Sir: Under date of June 11, 1857, I sent you a letter, to- 

 gether with some meteorological registers and a number of tables and 

 diagrams, which you probably will have received in due time. In- 

 closed I send you now — 



No. 1. Registers of meteorological observations for seven months, 

 viz : from June to December, 1857, inclusive. 



No. 2. A table showing by the length of horizontal lines at what 

 time of the day it rained at Colonia Tovar for each day from June to 

 December, 1857, inclusive. 



No. 3. A table containing a recapitulation of the occurrence of 

 rain expressed in number of hours, for all the months from July, 

 1856, to December, 1857, from 6 a. m. to 10 p. m. This table also 

 shows by the length of straight lines the comparative value for 

 each month, as regards the number of hours of rain ; and in another 

 diagram the mean rain value for each hour from 6 a. m. to 10 p. m. 



It may not be uninteresting here to see what a symmetrical figure 

 the curve a b c represents ; how it rises gradually from 6 a. m. to the 



