Page:Popular Science Monthly Volume 61.djvu/454

448 or deficient temperatures were indicated at cities within districts of too high or too low temperature, respectively. Similarly, the depressing effects upon trade of too much, or too little, precipitation were found in those portions of the country where there had been an excess or a deficiency of rainfall. So close were these relations in some weeks that it was possible to state in degrees, or in inches, the amount of the excess or deficiency of temperature or of rainfall which were needed to stimulate or to depress trade (e. g., the third week in June; and the weeks ending September 21 and April 14). So close an agreement is, however, exceptional. A careful study for the year in question of all the trade reports in which mention was made of weather control, and a close comparison of these reports with the temperature and rainfall charts, failed to give any such exact results as were hoped for.

The final outcome of this consideration may be briefly stated as follows: As the result of the experience of many years, trade is in a condition of such very close and delicate adjustment to the average weather of any particular month, or even week, that 'seasonable,' i. e., normal weather, other things being equal, usually means 'seasonable' trade. The case is not unlike that of a row of card houses which, when left undisturbed, i. e., under normal conditions, stand, but when interfered with by any unexpected or abnormal influence, fall down. Thus, when meteorological conditions are unseasonable, trade at once reflects the change, and suffers. Trade is, however, subject to many and widely-varying controls; hence the problem of the particular controls which affect it in any one week is a very complex one, and the key is not always, or sometimes even at all, to be found in local weather conditions. The trade of a city is often largely dependent upon orders coming from a distance. Hence, although the weather in the city may be unfavorable, and local trade depressed, orders from the tributary district may suffice to overcome this depression, and keep trade up to its usual standard, and vice versa. Again, while seasonable weather promotes active trade among the inhabitants of a city, the farmers round about may take advantage of this opportunity to work in their fields, and trade in the country districts suffers because the farmers are too busy to make purchases. Furthermore, the relation between temperature and precipitation on the one hand, and crops on the other (and hence, indirectly, the control of weather over trade) cannot be expressed in any simple way. This is partly because the effect of the weather of any one week upon crops, and upon trade, depends largely on the weather of the preceding weeks. Thus, if there has been enough rain, high, or even unusually high, temperatures may be needed to promote the growth of crops, while on the other hand, if the rainfall has been deficient, high temperatures may be very injurious. The proper distribution, in time and in amount, of temperature and precipitation in their relation to crops is a subject which itself still needs much careful study.