METEOROLOGY. 187 



of a mile in width, -which forms a Idncl of shallow hasin, only spar- 

 ingly covered by a thin coat of short grass and oUier small plants. 

 These ])lants I found the next morning at six o'clock white and 

 stiffened with heavy hoar frost, which augmented and lasted till the 

 rays of the sun fell upon it. The stiffened leaves of the herbs broke 

 under the least pressure, like thin layers of ice. The thermometer 

 was 37° at 67i. 30m. From all the information I could gather, hoar 

 frost seems to be common in this spot throughout the months of Janu- 

 ary and February. The wind blew during the night from northeast, 

 and was very })iercing. 



Notwithstanding this low temperature, the forests of the neighbor- 

 ing heights surrounding this basin are clothed in perpetual green, 

 and the stately wax palm, with its straight and polished trunk of 

 70 or 80 leet, (by actual measurement,) rears, uninjured, its slender 

 form and its leaf adorned head high above all other trees. 



In this excursion I had also an opportunity to form some idea of the 

 vast extent of destruction which was carried into the mountain forest 

 last February by a lucifer match and a thoughtless boy. Over whole 

 tracts of this primeval forest the trees lie dead one over the other, as 

 if uprooted by a whirlwind, scarcely showing any marks of fire on 

 their trunks. I was struck more than ever with the easy manner in 

 which fire can destroy these dense and humid forests, which, by cheir 

 shade, preserve a cool and moist atmosphere, and thereby cause the 

 vapors ox the adjacent strata of air to condense into clouds, that rest 

 upon them, with little intermission, during nine months in the year. 

 In these high regions the temperature is so low and equable that the 

 vegetable matter which is gathered on the ground between the trees 

 is decomposed very incom])letely and very slowly. It forms a stratum 

 of loose half-decomposed matter, in some places two to three feet thick, 

 which, in the rainy season, like an immense layer of sponge filled, 

 with water, feeds and supplies the rivulets and rivers gradually. In 

 the midst of the dry season this layer becomes sometimes dry enough 

 to burn, when kindled, with but little flame, and more like tinder, 

 spreading in all directions. 



In this way the fire extends until met by a river or a road, or some 

 other obstacle. The sub-soil which underlies the spongy stratum on 

 these mountains is also very shallow and resting on hard rocks. The 

 roots of the trees therefore, do not go down very deep, but extend 

 more in a horizontal direction. When the spongy layer, with the 

 smaller roots, are burnt, the trees lose their hold entirely and I'all, one 

 over the other, in all directions. They die less from being burnt than 

 from being uprooted. Many different kinds of tall reeds soon take 

 the place of the trees. In a few years these reeds exclude everything 

 else. The fertile mould that may perhaps have escaped destruction 

 by fire is by and by carried down the declivities by the frequent rains. 

 The region, no longer sh-^ded by high trees, becomes diy. Subse- 

 quent conflagrations of adjacent savannahs, which are intentionally 

 set on fire to procure a new growth of young grass, take hold of the 

 reeds of the ruined forest, until, by the repeated attacks of these fires, 

 the roots of the reeds can stand it no longer, and the smaller grasses, 

 interspersed with a lew other plants, take their places. 



