Miss Semple, following but improving upon Ratzel, has shown in turn the influences of geographical location, area, and boundaries upon people. She indicates the various ways in which oceans, rivers, and coast lines have molded human minds; she distinguishes between mountain, steppe, and desert effects upon mankind. She describes man as a product of the earth’s surface. She stresses unduly the physical influences; she considers nature the dominating force. Even where civilized man has developed inventive powers and spiritual prowess, nature is given the credit.[XV-14] Nevertheless, Miss Semple has marshalled facts in powerful array and increased their force by literary skill. No student or teacher can afford to neglect Miss Semple’s extensive survey of the interactions between physical nature and human progress. Among the many other writers upon the relation of geographic factors to civilization the investigations of Ellsworth Huntington are significant.[XV-15] He has described the climatic conditions that are most favorable to mental stimulation and growth, and then has classified all districts of the earth according to the degree in which they stimulate or arrest mental advance. In this same connection William Z. Ripley has investigated the relation of climate to races.[XV-16] After analyzing races and distinguishing between them and the geographic influences upon pigmentation, head, form, stature, and other traits, mainly structural, he classifies climatic elements in order of importance, as follows: humidity, heat, and monotony. A high humidity, excessive heat, and long series of sunshine or of cloudy weather produce mental enervation, stagnation, and retrogression. Acclimatization of races is a very slow process, according to Ripley. It requires centuries. Perhaps the white race can never become truly acclimated in the tropics. Racial differences he shows are due to environmental factors far more than is ordinarily supposed. In conclusion, it may be said that physical forces have operated strongly on man. But when man has developed modern mental tools, he has been able to escape a part of the enslaving environmental influences. The history of the relation of geographic factors to human progress indicates a fundamental but a proportionate decrease in those influences. CHAPTER XVI SPENCER AND ORGANIC SOCIAL THOUGHT In the second half of the last century social thought passed under biological influence. Society was discussed in terms of biological analogies, that is, it was compared in its structure and functions to organic life. Herbert Spencer was the leader among those writers who attempted to analyze society in terms of biological figures of speech. He also stressed the structural nature of society, and in his _Principles of Sociology_ he went into great detail in giving a historical description of social institutions.