PREFACE TO THE THIRD VOLUME

Summary

It may be questioned, whether woods are to be considered any further detrimental to the air of their neighbourhood, than as they may obstruct the free passage of refreshing gales?

It is the opinion of an ingenious gentleman, who resided for many years in the West-Indies, that local unhealthiness in that part of the world has been most remarkable on spots newly cleared of their native woods; that for this reason, a residence there is generally unwholsome to the first settlers, though not always so to the first cultivators. The land in such places is covered to some depth with a mould, which has been gradually deposited and encreased by the trees, plants and vegetables, springing up, growing and rotting upon the surface for ages; so that an accession of soil has been gained every year, by the successive decay of these vegetable races. While it continues overshadowed with thick forests, equally impervious to the sun and winds, the soil lies in a kind of inactive state; but no sooner is it laid open to those influences, and the copious absorption of dews and showers, charged with volatile, putrefactive particles, than a ferment or intestine motion is excited; and vapoury steams begin to ascend in great abundance, which are prejudicial to human health. So, after these opened spots have lain for some space of time thus exposed, the fermentation gradually subsides, and, the materials which gave birth to these pernicious effluvia being exhausted, the air becomes amended, and the mortality ceases with the causes of it.