AGRICULTURE WITH CHEMISTRY. 33

the trees had been thrown down, and causing a stoppage of the waters in their passage to the sea, the growth and decay of the aquatic vegetables already described, had formed.those extensive peat mosses and fens, which, in their natural state, are of all soils the most unproduc-

tive, but which are the most fertile when improved.

Peat is very retentive of moisture, retaining it in a manner similar to that of aspunge. At no time, there-

fore, in this humid and northern climate, can such soils

be divested of their superabundant proportion of mois- ture with which they charge themselves in the autumn, spring, and winter, as well as during the periodical rains in summer. The sun’s rays, or drying winds, during the summer season, are exerted in conveying away, by eva- poration, this surplus moisture; and as heat is known

to be abstracted from bodies, and cold generated by eva-

poration, hence effects will arise injurious not only to climate, but likewise to vegetation in general; but more especially so to such plants as require a greater degree of heat and nourishment, than soils of the above descrip- tion will admit of.. There can be little doubt, that these

injurious effects on vegetation will extend themselves

E even