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have not the same intensity. The intensity of each ray is proportional

1 Each paragraph of the Table indicates the matter treated of in the articles
indicated at the left of that paragraph. The first of these articles begins at
the page marked on the right.

PAGE

ART.

to the cosine of the angle which its direction makes with the normal to
the surface. Divers remarks, and considerations on the object and extent
of thermological problems, and on the relations of general analysis with
the study of nature.

22

in liquids . . .

38, 39. Equilibrium of temperatures. The effect is independent of contact. 32

40—49. First notions of radiant heat, and of the equilibrium which is

established in spaces void of air ; of the cause of the reflection of rays
of heat, or of their retention in bodies; of the mode of communication
between the internal molecules; of the law which regulates the inten.
sity of the rays emitted. The law is not disturbed by the reflection of
heat.

ib.

50, 51. First notion of the effects of reflected heat

• 37

52–56. Remarks on the statical or dynamical properties of heat. It is the

principle of elasticity. The elastic force of aeriform fluids exactly indi-

cates their temperatures.

39

SECTION II.

PRINCIPLE OF THE COMMUNICATION OF HEAT.

57—59. When two molecules of the same solid are extremely near and at

unequal temperatures, the most heated molecule communicates to that
which is less heated a quantity of heat exactly expressed by the product
of the duration of the instant, of the extremely small difference of the
temperatures, and of a certain function of the distance of the molecules .

ib.

45

48
61

53

ib.
55

SECTION V.
LAW OF THE PERMANENT TEMPERATURES IN A PRISM OF SMALL THICKNESS.

.

THE HEATING OF CLOSED SPACES.

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The value of P is

g

ge

I

+ +

A

K I

m is the temperature of the internal

air, n the temperature of the external air, g, h, H measure respectively
the penetrability of the heated surface o, that of the inner surface of the
boundary s, and that of the external surface 8; e is the thickness of the

boundary, and K its conducibility proper .

85, 86. Remarkable consequences of the preceding equation .

87–91. Measure of the quantity of heat requisite to retain at a constant

temperature a body whose surface is protected from the external air by

62

65

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EQUATION OF THE VARIED MOVEMENT OF HEAT IN A Ring.

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