And by the influence of heat, light, and electrical powers, there is a constant series of changes [in animal and vegetal substances]; matter assumes new forms, the destruction of one order of beings tends to the conservation of another, solution and consolidation, decay and renovation, are connected, and whilst the parts of the system, continue in a state of fluctuation and change, the order and harmony of the whole remain unalterable.

COLD. Healthier than heat.

Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time.

Heat is a motion; expansive, restrained, and acting in its strife upon the smaller particles of bodies. But the expansion is thus modified; while it expands all ways, it has at the same time an inclination upward. And the struggle in the particles is modified also; it is not sluggish, but hurried and with violence.

If this fire determined by the sun, be received on the blackest known bodies, its heat will be long retain'd therein; and hence such bodies are the soonest and the strongest heated by the flame fire, as also the quickest dried, after having been moisten'd with water; and it may be added, that they also burn by much the readiest: all which points are confirm'd by daily observations. Let a piece of cloth be hung in the air, open to the sun, one part of it dyed black, another part of a white colour, others of scarlet, and diverse other colours; the black part will always be found to heat the most, and the quickest of all; and the others will each be found to heat more slowly, by how much they reflect the rays more strongly to the eye; thus the white will warm the slowest of them all, and next to that the red, and so of the rest in proportion, as their colour is brighter or weaker.

In all cases where work is produced by heat, a quantity of heat proportional to the work done is expended; and inversely, by the expenditure of a like quantity of work, the same amount of heat may be produced.

The fundamental laws of the universe which correspond to the two fundamental theorems of the mechanical theory of heat.
1. The energy of the universe is constant.
2. The entropy of the universe tends to a maximum.

The production of motion in the steam engine always occurs in circumstances which it is necessary to recognize, namely when the equilibrium of caloric is restored, or (to express this differently) when caloric passes from the body at one temperature to another body at a lower temperature.

There is deposited in them [plants] an enormous quantity of potential energy [Spannkräfte], whose equivilent is provided to us as heat in the burning of plant substances. So far as we know at present, the only living energy [lebendige Kraft] absorbed during plant growth are the chemical rays of sunlight... Animals take up oxygen and complex oxidizable compounds made by plants, release largely as combustion products carbonic acid and water, partly as simpler reduced compounds, thus using a certain amount of chemical potential energy to produce heat and mechanical forces. Since the latter represent a relatively small amount of work in relation to the quantity of heat, the question of the conservation of energy reduces itself roughly to whether the combustion and transformation of the nutritional components yields the same amount of heat released by animals.

What signifies Philosophy that does not apply to some Use? May we not learn from hence, that black Clothes are not so fit to wear in a hot Sunny Climate or Season, as white ones; because in such Cloaths the Body is more heated by the Sun when we walk abroad, and are at the same time heated by the Exercise, which double Heat is apt to bring on putrid dangerous Fevers? The Soldiers and Seamen, who must march and labour in the Sun, should in the East or West Indies have an Uniform of white?