Finally, the aspect of meteorology that has thus far acquired the most definite shape in medical circles and given rise to the most coherent body of literature is Medical Climatology, which is designed to be applied in the climatic treatment of disease (climatotherapy). Thus many compilations have been made of the climatic statistics of health resorts, and these resorts have been classified with respect to their supposed climatic effects upon various diseases. From the point of view of the physical climatologist, the statistics found in such books seem, in general, both meager and ill adapted to bring out important features of the climates discussed; to say nothing of the fact that the whole subject of climatotherapy is fraught with controversy--whereof the history of the treatment of tuberculosis furnishes a shining example! CHAPTER XXI WEATHER-MAKING Meteorologists, in their candid moments, have been heard to express disappointment over the amount of progress made in the art of weather forecasting during the past half-century. “Shall we ever,” they ask, “be able to predict the weather with mathematical certainty, as the astronomer predicts an eclipse of the sun or moon?” Perhaps even within the meteorological fold there are unorthodox optimists who would answer such a question thus: “Yes, because some day we shall _control_ the weather. It is inconceivable that man, who is every day achieving new miracles in the conquest of nature, should not eventually find a way of regulating the rainfall and sunshine that are of such vital importance to his crops, the winds that must be reckoned with in his voyages by sea and air, and the various other elements of weather that have so much to do with his happiness and welfare. The attainment of this object is so tremendously desirable that it cannot forever baffle human ingenuity.” In support of such a bold assertion it might be pointed out that we already control the weather to a certain limited extent. When the horticulturist burns orchard heaters to protect his fruit from frost he certainly alters the weather for a few hours over a small area of the earth. If there were any practical justification of the process, the temperature of the air over an entire State, for example, could be raised throughout the winter, with appreciable effects on agriculture. The difference between heating a single orchard for a night and heating a State for a season is one of degree, and not of principle.