2. If all countries were equally warm, all horses would grow the same thickness of coat.
3. If all countries had equal moisture, all horses would show similar endurance.
4. If all countries had one type of landscape, all horses would show the same markings.
5. If all countries had one soil, all horses would be of one build.
6. If all countries had one weight of forage to the acre, all horses would have one bulk.
7. If all countries had one quality of forage, all horses would have one strength.
8. It follows that the study of light, heat, moisture, landscape, soil, and food should explain the origin of the wild types of horses. Our breeds are got by crossing from these varieties.
If, therefore, the facts which we find out by study shall correspond with the reader's own experience of horses, no further proof is needed; but if they fail to appeal to the reader's sense and judgment, no balancing of proofs upon a point of falsehood will save a useless book from the flames which await waste paper.
PART I. COLORATION BY SUNLIGHT.