[29] Walker's History of the Creation, p. 8, 9.
[31] Preface to Dr. Black's Lectures, by Robison.
[32] Carpenter's Lectures on the Works of Creation, vol. i. p. 87.
[33] Boerhaave's Chem. by Shaw, vol. i. p. 299.
[34] Parkes's Chemical Catechism, or Rudiments of Chemistry, chap. ii.
[35] Contemplative Philosopher, vol. ii. p. 149, 150.
[36] See Dr. Burnet's Theory, vol. ii, p. 30.
[38] That light is a fluid which encompasses the earth, and requires only to be agitated by some other inflamed body, in order to render it perceptible, is an hypothesis, says a celebrated German divine, that has been adopted by the most eminent philosophers. "It is certain, at least, that there is a great difference between _fire_ and _light_. The latter is incomparably more subtile than the former. It penetrates glass, and other transparent bodies, in a moment; whereas fire does it very slowly. The pores of glass are consequently large enough to give a free passage to the light, while the fire meets with more resistance, because it is less subtile. Fire moves more slowly than light. Let burning coals be brought into a room, the heat diffuses itself very slowly, and the air becomes warm by degrees; but the moment a candle is brought into an apartment, the whole is suddenly illuminated; and wherever the rays can reach the parts become more visible. From these facts, and some others, it is concluded, that fire and light are different substances; although we generally see them both together, and find that one may produce the other. But the consequence drawn from this is possibly false."
[39] A new material has recently been introduced in this country, for the purpose of lighting houses, streets, manufactories, &c, namely, the inflammable gas of coals. When coals are burning in a common fire-place, a flame more or less luminous, according as it is more or less encumbered with incombustible smoke and vapor, issues from them; and very frequently emit some very beautiful streams of a flame remarkably bright. All this arises from the gases which are extricated from the coal by the heat. It was natural to imagine that such gas might be received in proper reservoirs, and, on being forced out of small apertures, and lighted, would serve, as the flames of candles, to illuminate rooms or other places. The trial was easily made, and has been attended with the desired effect.