prefixed, a short Account of the Author, written by him

self. Lond. 1773, 8vo. 5s. The Art of Drawing in Perspective, made easy to those

who have no previous knowledge of Mathematics. Plates.

Lond. 1775, 8vo. 3s. 6d. The Phenomena of Venus, represented in an Orrery. Phil.

Trans Abr. ix. 226. 1746. An improvement of the Celestial Globe. Ib. 351. 1747. Description of a piece of Mechanism contrived by him, for

exhibiting the Time, Duration, and Quantity of Solar Eclipses, in all Places of the Earth. Ib. x. 456. 1749.

Mr. Ferguson calls this machine an Eclipsareon. A Delineation of the Transit of Venus, expected in the year

1769. Ib. xi. 685. 1763. Of a remarkable Fish taken in King's Road, Bristol. Ib.

717. 1763. The Long Angler of Pennant, or Sophius

Conubicus of Shaw. On the Eclipse of the Sun, April 1, 1764. Ib. xii. 5. 1763. Description of a new Crane which has four different

powers. Ib. 86. 1764. Observations made at Liverpool of the Lunar and Solar

Eclipses. Ib. 113. 1764. Description of a new Hygrometer. Ib. 161. The quantity of time in any number of Lunations, &c. So &c. Ib. 197. 1765.

. A new Method of constructing Sun-dials, for any giveu

Latitude, without the assistance of Dialing Scales, er Logarithmic Calculations. Ib. 454. 1767.

ON

SELECT SUBJECTS.

LECTURE I.

OF MATTER AND ITS PROPERTIES.

1.

what.

AS the design of the first part of this course is to ex- LECT. plain and demonstrate those laws by which the material universe is governed, regulated, and continued ; and by which the various appearances in nature are accounted for; it is necessary to begin with explaining the properties of matter.

By the word matter is here meant every thing that Matter, has length, breadth, and thickness, and resists the touch. The inherent properties of matter are solidity, in- Its proper

ties. activity, mobility, and divisibility.

The solidity of matter arises from its having length, Solidiiy breadth, thickness; and hence it is that all bodies are comprehended under some shape or other, and that each particular body hinders all others from occupying the same part of space which it possesseth. Thus, if a piece of wood or metal be squeezed ever so hard between two plates, they cannot be brought into contact. And even water or air has this property; for if a small quantity of it be fixed between any other bodies, they cannot be brought to touch one another.

Note 1. By solidity or impenetrability in common language, is uu. derstood the property of not being easily separated into parts, -a

B

LECT.

J.

A second property of matter is inactivity or passiveness; by which it always endeavours to continue in the Inactivity. state that it is in, whether of rest or motion. And therefore, if one body contains twice or thrice as much matter as another body does, it will have twice or thrice as much inactivity; that is, it will require twice or thrice as much force to give it an equal degree of motion, or to stop it after it hath been put into such a motion.

That matter can never put itself into motion is allowed by all men. For they see that a stone, lying on the plane surface of the earth, never removes itself from that place, nor does any one imagine it ever can. But most people are apt to believe that all matter has a propensity to fall from a state of motion into a state of rest; because they see that if a stone or a cannon-ball be put into ever so violent a motion, it soon stops; not considering that this stoppage is caused, 1. By the gravity or weight of the body, which sinks it to the ground in spite of the impulse; and, 2. By the resistance of the air through which it moves, and by which its velocity is retarded every moment till it falls.

A bowl moves but a short distance upon a bowlinggreen; because the roughness and unevenness of the grassy surface soon creates friction enough to stop it. But if the green were perfectly level, and covered with polished glass, and the bowl were perfectly hard, round, and smooth, it would go a great way farther, as it would have nothing but the air to resist it; if then the air were meaning differing very materially from that of our author in the above paragraph; who would shew rather that as every thing which is material must possess length, breadth, and thickness, these properties cannot exist without the occupation of space, and as such, that even air which is invisible, and eludes the grasp, no less than the vision of the philosopher, may be so compressed as to attain a perfectly solid form. To illustrate experimentally the materiality of air it is merely necessary to invert a wine glass in & "essel of water, and the aeriform fluid within, will prevent the introduction of the water, which would enter immediately if the air was allowed to escape.

.

taken away, the bowl would go on without any friction, LECT. and consequently without any diminution of the velocity it had at setting out: and therefore, if the green were extended quite around the earth, the bowl would go on, round and round the earth, for ever.

If the bowl were carried several miles above the earth, and there projected in a horizontal direction, with such a velocity as would make it move more than a semidiameter of the earth, in the time it would take to fall to the earth by gravity ; in that case, and if there were no resisting medium in the way, the bowl would not fall to the earth at all ; but would continue to circulate round it, keeping always in the same tract, and returning to the same point from which it was projected, with the same velocity as at first. In this manner the moon goes round the earth, although she be as inactive and dead

stone
upon

it. The third property of matter is mobility; for we find Mobility. that all matter is capable of being moved, if a sufficient degree of force be applied to overcome its inactivity or resistance.

The fourth property of matter is divisibility, of which Divisibl there can be no end. For, since matter can never be lity. annihilated by cutting or breaking, we can never imagine it to be cut into such small particles, but that if one of them be laid on a table, the uppermost side of it will be further from the table than the undermost side. More

as any