Of Tin109

Of the Semi-metals113

LECTURE XXVII.

Of Nickel115

Of Arsenic116

Of Cobalt118

Of Zinc119

LECTURE XXVIII.

Of Antimony121

Of Manganese123

Of Wolfram124

Of Molybdena125

Of Solid Combustible Substances126

LECTURE XXIX.

Of the Doctrine of Phlogiston and the Composition of Water127

LECTURE XXX.

Of Heat135

LECTURE XXXI.

Of Animal Heat145

LECTURE XXXII.

Of Light148

LECTURE XXXIII.

Of Magnetism155

LECTURE XXXIV.

Of Electricity162

[Pg xxviii]

LECTURE XXXV.

The same Subject continued170

LECTURE XXXVI.

The same Subject continued177

LECTURE I.

The Introduction.

The object of experimental philosophy is the knowledge of nature in general, or more strictly, that of the properties of natural substances, and of the changes of those properties in different circumstances. This knowledge can only be attained by experiment, or observation; as that clay is capable of becoming hard by means of fire, and thereby being made into bricks, and that by the same means lime-stone can be converted into quick-lime, and by the addition of water and sand, make mortar. It is by observation also that we discover that stones and other heavy bodies fall to the ground, and that a magnet will attract iron. In other words, experimental philosophy is an investigation of the wisdom of God in the works and the laws of nature, so that it is one of the greatest objects to the mind of man, and opens a field of inquiry which has no bounds; every advance we make suggesting new doubts and subjects of farther inquiry.

The uniformity we discover in the properties of natural substances enables us to lay down general rules, or principles, which, being invariable, we call the laws of nature; and by our knowledge of these laws we are able to predict, and at our own pleasure to produce, particular results, and this is the source of all the powers of man. It is the direction we acquire of the powers of nature; so that, as Lord Bacon observed, knowledge is power.

All arts and manufactures are derived from science. Thus the doctrine of mechanics is an application of the law of gravitation. Every thing we are capable of doing by means of the steam-engine is derived from our knowledge of the properties of water in steam; all the great effects of gunpowder we owe to our knowledge of the composition, and chemical properties, of that substance.

Every new appearance in nature is preceded by some new circumstance, and to this, or rather to something always attending it, we say that the appearance is owing. This circumstance we therefore call the cause, and the new appearance the effect of that cause. Thus we say that the union of phlogiston to a particular kind of earth is the cause of its becoming a metal.

It is one of the principal rules of philosophizing to admit no more causes than are necessary to account for the effects. Thus, if the power of gravity, by which heavy bodies fall to the earth, be sufficient to retain the planets in their orbits, we are authorized to reject the Cartesian Vortices. In other words, we must make no more general propositions than are necessary to comprehend all the particulars contained in them. Thus, after having observed that iron consists of a