Bodies of different colours convey heat also differently. The difference between white and black is well known; and the more intense colours, as red, orange, etc. convey it more readily than the blue or indigo. If heat and light are distinct bodies, as is now generally supposed, and light only excites the action of caloric, we can easily understand why bodies which reflect all, or the greater proportion of light, excite little heat. Count Rumford, in the Philosophical Transactions for 1804, has shown, that blackening a cylinder expedited the cooling of water in it: in fact, the communication of heat from bodies to air is slow, and an intermede of less density, if no air is interposed between its particles, facilitates it. Another reason of this unexpected effect is the destruction of the polish. Polished surfaces communicate heat slowly; and this is an additional reason for the warmth of furs, whose fibres possess a high polish. For this reason silk clothes are cold; and even black clothes, in this author's opinion, in the shade, are cooler than those of other colours.

Of specific and absolute heats we have already spoken at sufficient length. Specific heat, however, depends on the affinity between the body and caloric; and consequently is in the inverse ratio of their conducting power. We shall add, therefore, a table of the specific caloric of different bodies, collected from the tables of Mr. Kirwan. M. Meyer, and some others, by Dr. Thomson.

Table of the Specific Caloric of various Bodies, that of Water being =1.0000.

Bodies.

Specific Gravity.

Specific of equal weight.

Caloric of equal volumes.

I. Gases.

Hydrogen gas - - -

0.000094

21.4000

0.00214

Oxygen gas - -

0.0034

4.7490

0.006411

Common air ...

0.00

1.7900

0.002183

Carbonic acid gas - -

0.00183

1.0459

0.001930

Steam .....

1.5500

Azotic gas ....

0.00120

0.7036

0.000952

II. Liquids.

Water...................

1.0000

1.0000

Carbonate of ammonia -

1.851

Arterial blood - - -

1.030

Cows' milk - - - -

1.0324

0.9999

1.0322

Sulphuret of ammonia -

0.818

0.994O

0.8130

Venous blood - - -

0.8928

Solution of brown sugar

0.8600

Nitric acid - - - -

0.844

Sulphat of magnesia 1

0.844

Water - - - - 8

Common salt 1

0.832

Water - - 8

Nitre 1

0.8167

Water 8

Muriat of ammonia 1

0.779

Water - - - - 1.5

Tartar 1

0.765

Water 237.3

Solution of potash - -

1.346

0.759

1.2216

Sulphat of iron 1

0.734

Water - - 2.5

Sulphat of soda 1

0.728

Water - - 2.9

Oil of olives - - - -

0.9153

0.710

0.6498

Ammonia ....

0.997

0.7080

0.7041

Muriatic acid - - -

1.122

0.6800

0.763

Sulphuric acid 4

0.6631

Water - - 5

Alum 1

0.649

Water 4.45

Nitric acid 9 1/3

0.6181

Lime - 1

Nitre 1

0.646

Water 3

Alcohol.............

0.8371

0.6021

0.4993

Sulphuric acid ...

1.840

0.5968

1.120

Nitrous acid ...

1.355

0.576

0.780

Linseed oil ....

0.9403

0.528

0.4964

Spermaceti oil - - -

0.5000

Oil of turpentine - .-

0.9910

0.472

0.4132

Vinegar..............

0.3870

0.3966

Lime 9

0.3346

Water 16

Mercury...................

13.568

0.3100

4.123

Distilled vinegar - -

0.1030

0.1039

III Solids.

Ice ---...

0.9000

Oxide with the hair

0.787

Lungs of a sheep - -

0.769

Lean of ox beef ...

0.7400

Bodies.

Specific Gravity.

Specific of equal weight.

Caloric of equal volumes.

Pinus sylvestris - -

0.108

0.65

0.265

Pinus abies - - - -

0.447

0.60

0.268

Tilea Europaea - - -

0.408

0.62

0.252

Pinus picea - - - -

0.495

0.58

0.287

Pyrus malus - - - -

0.639

0.57

0.364

Betula alnus - - - -

0.484

0.53

0.256

Quercus robur sessilis -

0.531

0.51

0.270

Fraxinus excelsior - -

0.631

0.51

0.321

Pyrus communis - -

0.603

0.50

0.301

Rice............

0.5050

Horse beans - - - -

0.5020

Dust of the pine tree -

0.5000

Pease.......

0.4920

Fagus sylvatica - - -

0.692

0.49

0.358

Carpinus betulus - -

0.690

0.48

0.831

Betula alba - - - -

0.608

0.48

0.291

Wheat--------

0.4770

Elm......

0.646

0.47

0.321

Quercus robur pedunculata----------

0.668

0.45

0.300

Prunus domestica - -

0.687

0.44

0.302

Diaspyrus ebenum

1.054

0.43

0.453

Barley------------

0.4210

Oats......

0.4160

Pitcoal------------

0.2777

Charcoal.....

0.2631

Chalk .....

0.2564

Rust of iron - - - -

0.2500

White oxide of antimony washed - -

0.2270

Oxide of copper nearly freed from air - -

0.2272

Quicklime ....

0.2199

Stoneware - - - -

0.195

Agate--------------

2.648

0.195

0.517

Crystal.....

3.189?

0.1929

0.6151

Cinders -----

0.1923

Swedish glass - - -

2.386

0.187

0.448

Ashes of cinders - -

0.1885

Sulphur - - - - -

1.99

0.183

0.3680

Flint glass - - - -

3.3293

0.174

0.5792

Rust of iron nearly freed from air - - - -

0.1666

White oxide of antimony ditto - - - -

0.1666

Ashes of the elm - -

0.1402

Oxide of zinc nearly free from air - - -

0.1369

Iron -------------

7.876

0.1264

0.993

Brass --------------

8.358

0.1141

0.971

Copper----------------

8.784

0.1121

1.027

Sheet iron - - - -

0.1099

Oxide of lead and tin -

0.102

Gun metal - - - -

0.1100

White oxide of tin nearly free from air - -

0.0990

Zinc......

7.154

0.0981

0.735

Ashes of charcoal - -

0.0909

Silver......

10.001

0.082

0.833

Yel. oxide of lead nearly freed from air - -

0.0680

Bodies.

Specific Gravity.

Specific Of equal weight

Caloric of equal volumes.

Tin......

7.380

0.0661

0.444

Antimony - - - -

6.107

0.0637

0.390

Gold......

19.040

0.050

0.966

Lead...........

11.456

0.0424

0.487

Bismuth - - - - -

9.861

0.043

0.427