Every important aspect of human knowledge must be considered in its relation to both space and time. In "Civilization and Climate" the problem of the effect of physical environment upon human progress was discussed in its relation to space. It was shown that the distribution of civilization upon the earth's surface is closely in harmony with the distribution of climatic energy, which appears to be the most important factor in physical environment. In the present volume the same problem is considered in its relation to time. Beginning with the present day we find that from year to year business activities vary in extraordinary harmony with health. Further study shows that variations in health from year to year depend upon the weather far more than upon any other single factor. - Summary by Ellsworth Huntington