displays itself in the movements of the planetary system; in the appearances of inanimate Nature; and, above all, in the structure and functions of animals and plants. Here, we find a skill and contrivance, which are worthy of the Most High, and which leave, at an infinite distance, the puny efforts of human art. What mechanic has ever yet formed an instrument, with the flexibility, delicacy, and force, of the human hand? What human artist ever yet gazed on a specimen of his own handiwork, like that which called forth the admiration of the Psalmist,-that frame, clothed with skin and flesh, and fenced about with bones and sinews, so wonderfully and fearfully made by the finger of Omnipotence! Indeed, the most distinguished inventors have been content to borrow hints for their operations from the humblest of the Creator's devices. When Smeaton had reflected long, in search of that form which would be best fitted to resist the combined action of wind and waves, he found it in the trunk of the oak. When Watt was employed to conduct a supply of water across the Clyde to the city of Glasgow, he borrowed his admirable contrivance of a flexible water-main from considering the flexibility of the lobster's tail; and so when Mr. Brunell was engaged in superintending the construction of the tunnel under the Thames, it was from observing the head of an apparently insignificant insect, that he derived his first conception of the ingenious shield, which he introduced in advance of the workmen, to protect them from being crushed by the falling in of the earth.

It becomes us, then, while we trace the operations of human ingenuity, in adapting means to its proposed ends, to raise our thoughts to that Divine Architect, who has imprinted traces of His wisdom and power on all His works: causing the heavens to declare His glory, and the earth, throughout all its domains of land, and sea, and air, to show forth His handiwork!

SUMMARY OF PRINCIPLES, IN PART II.

AGENTS EMPLOYED IN THE ARTS.

I. Chemical Agents.

i. They all depend on one principle called Affinity. 1. Affinity is the tendency which particles of different kinds have to unite, when brought very near each other.

2. (a) It causes, two fluids or gases, when shaken together, to intermingle, if they have affinity, forming a chemical compound.

(b) It causes solids, when placed in liquids for which they have an affinity, to dissolve. These solutions have the following properties. a They sensibly retain the properties of the ingredients. b A liquid can generally dissolve only a certain quantity of a solid. c Having dissolved a portion of one solid, it can afterwards do the same for another and different solid. d It will precipitate any solid, which it may hold in solution, provided another, for which it has a stronger affinity, be presented, and will unite with the second. This is called elective affinity. When there is but one decomposition, and one new composition, it is called single elective affinity. When there are two, it is called double elective affinity.

ii. (a) Affinity also causes a more intimate union between bodies, giving rise to more energetic action, and producing new properties. These compositions have the following properties: a The ingredients wholly disappear, and entirely new characters are developed. b The nature of these characters depends on the proportion in which the ingredients combine; different proportions giving rise to entirely different substances, or compounds. c The number of proportions, in which the same ingredients combine, is definite and small,

being always capable of being represented by a number, or by some multiple of that number.

Observation. The proper management of this principle constitutes much of the art of the tanner, bleacher, dyer, &c. &c.

II. Mechanical Agents.

1. Chemical agents act only at insensible distances, and change only the interior structure of bodies.

2. Mechanical agents act, on the contrary, at sensible distances, and change only the position or form of their masses.

To understand the nature of these agents, we must familiarize our minds to the three fundamental laws of motion. Namely,

i. Masses of matter never change their state of rest or motion, unless some force be impressed upon them.

ii. This change is always proportioned to the force, and in the direction of this force.

iii. To every action of one body upon another, there is an equal and contrary reaction. The mechanical agents are, animate and inanimate forces.

1. Animate forces consist of the strength of men and animals.

(a) The time in which they can be exerted is necessarily limited.

(b) The manner must be determined by the structure and habits of the animal.

(c) The relative value of different animals depends on the expense of keeping them, the amount of force they can exert, and the variety of ways in which they can be used; from which we infer, that, of all animate forces, that of man is the least useful, and that of the horse the most so.

II. The inanimate forces are, gravity, elasticity, and heat.

i. Gravity.

(a) Gravity acts on solids, as on bodies falling through

space, descending inclined planes, &c., and causes them to move with a uniformly accelerated velocity.

(b) Gravity acts on water in the case (1) of waterwheels; (2) of water flowing through orifices, tubes, canals, &c.; (3) by hydrostatic pressure, in case of the hydrostatic bellows, and of Brahmah's press; of water rising to its own level in bent tubes; and of the method of specific gravity discovered by Archimedes. (c) Gravity acts on air, in the case of the common pump, barometer, windmills, &c.

ii. Elasticity acts on air, in the case of fire engines, airpumps, airguns, &c.

iii. Heat acts as a mechanical agent.

1. By expanding bodies, as in metals.

This property of heat gives rise to instruments for measuring the degrees of it, as the thermometer and pyrometer.

2. Heat acts as a mechanical agent, by changing the form of bodies, as in steam.

The numerous other important uses of heat, in the arts, call for improvements in the prevailing and very defective modes of generating and supplying it.

MACHINERY EMPLOYED IN THE ARTS.

i. Its existence is to be attributed, 1. To man's want of natural implements; 2. To the admirable provision made, for the invention and construction of machinery, in the ingenuity of man's mind and the conformation of his hand.

ii. All machines, however complex, are composed of certain elements, called simple machines, namely, the lever, the wheel and axle, the inclined plane, the screw, the wedge, the pulley and rope.

iii. The various and complex machinery, which has been formed by combining these elements, is useful:

1. As enabling us to overcome great resistances, by diminishing their velocity, and operating upon them for a length of time.

2. As enabling us to change the direction of the moving force.

3. As enabling us to vary the velocity of the resistance, especially by increasing it.

4. As enabling us to regulate, or render uniform, the motion of the machinery.

5. As enabling us to accumulate force, to be expended instantaneously, or through a long series of separate actions.

6. As enabling us to employ a vast amount of force, which would otherwise be lost.

7. As it enables us to render our work more exact, and the different specimens more identical.