IV

PREFACE*

Natural or mechanical philosophy seems to considerbodies chiefly as being entire aggregates or masses; as be-ing divisible into parts, each of the fame general propertieswith the whole; as being of certain magnitudes or figures,.known or investigable > gravitating, moving, resisting, &c.with determinate forces, subject to mechanic laws, and re-ducible to mathematical calculation.

Chemistry considers bodies as being composed os’such a particular species of matter;'dissoluble, liquefiable,,vitrescible, combustible, fermentable, &c*. impregnatedwith colour, smell, taste, &c. or consisting of dissimilarparts, which may be separated from one another, or trans-ferred into other bodies.. The properties of this kind arenot subject to any known mechanism, and seem to begoverned by laws of another order.

To the grand active power,, called attraSHon, in themechanical philosophy, what corresponds in the chemicalis generally distinguished by another name, affinity.

The mechanical attraction obtains between bodies con-sidered each as one whole, and between bodies of the fameas well as of disserent kinds. It obtains while the bodiesare at sensible distances; and the comparative forces, withwhich they tend together at different distances, are objectsof calculation. When the attracting bodies have comeinto the closest contact we can conceive, they still continuetwo distinct bodies, cohering only superficially, and sepa-rable by a determinate mechanic force.

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