Microscopic Creatures as part of Man's Environment.—Since the microscope was invented people have learned the importance of tiny germs including both the minute animals called "protozoa," such as produce malaria, and the equally small plants called bacteria, such as spread typhoid fever. These tiny creatures are a part of man's geographic surroundings as much as the bigger forms of life such as horses, tigers, fish, and insects, or trees, bushes, grass, and corn. Because the protozoa and bacteria, however, can be seen only under a powerful microscope and are known only by the results they produce they were long ignored. Their effects upon man, however, are fully as important as those of the larger forms of life, as is clear from the examples of diseases which we have just considered. Man must study the minuter forms of life with special care because of their great variety, and because they are so variable in their activity. He can plan to meet the attacks of tigers and wolves, but it is harder to meet the attacks of tiny creatures so small and numerous that we may take them in by the million at every breath and so deadly sometimes that they kill a thousand men where wild animals kill only one.
The Newfoundland Fisheries.—Thus far in considering geograph ical variables we have concerned ourselves largely with pests. Let us now look at the movements of useful animals such as the fish of the Newfoundland Banks. More than half of the people of Newfound land are engaged in catching and curing fish. The total catch varies greatly from year to year because of changes in the fishes' food supply, in the amount of salt in the water, and in conditions of temperature, storminess, and winds. Hence the island sometimes enjoys prosperity and sometimes suffers distress. From about 1860 to 1868 the New foundland fisheries were so unproductive that widespread destitution prevailed among the working classes. Hence people began to turn to agriculture and stockraising and farming received such a start that it has increased ever since, in spite of the cool climate. This is for tunate, for Newfoundland cannot prosper unless other resources beside fishing are exploited. A less favorable result was the introduction of a system of poor relief, not only for people who were unable to work, but for the able-bodied. This proved very demoralizing, for people said that if the government would support them, they were not going to work. Even though the fisheries became successful again in 1869 the poor relief system had lasted long enough to do serious harm.
Weather as a Geographic Variable. The Galveston Hurricane.—
Many geographic variables such as insect pests, epidemics, and the migrations of fish are due indirectly to the weather. The direct effects of variations in the weather are equally important. For in stance, in September, 1900, Galveston, Texas, was visited by a hurri cane from the West Indies. A violent wind blew for eighteen hours, reaching a maximum velocity of 84 miles an hour. The waters of the Gulf of Mexico were piled up in enormous waves that swept across a large part of the city, destroying or badly damaging more than 8000 buildings, and entailing the loss of about 6000 lives and of property valued at $30,000,000. Thereupon the city set to work to prepare for the recurrence of this variable geographic condition. A wall of solid masonry was built for 5 miles along the water front at an expense of $2,000,000. The entire grade of the city was raised from 1 to 15 feet above its former level.
In August, 1915, there came another hurricane nearly as violent as that of 1900. The maximum velocity of the wind was 93 miles per hour, but the tide at the highest rose only 12 feet instead of 20 as in 1900. Thanks to the seawall and to the warnings sent by the Weather Bureau to people living beyond the protection of the wall the loss of life in 1915 was only about 275, while the property loss was -much less than before.
Rainfall and Settlement in Kansas.—Rainfall is another element of weather, the variations of which are of great importance. In western Kansas, for example, the corn crop depends on the summer rain, especially that of July, when the ears are developing most rapidly. The curved line of Fig. 115 shows how the variations of the rainfall of May, June, and July have affected the farmers of western Kansas since 1870. When the curved line is above the straight line repre senting the average rainfall the farmers prosper. When it falls below, they often cannot raise enough to support their families and pay their The meager rainfall from 1870 to 1877 did little harm, for then there were few settlers in western Kansas, and most of them depended upon cattle more than on crops. Even among these, however, some became so poor that they had to move away. The period from 1878 to 1886 was excellent, for the rainfall was abundant, Settlers moved into western Kansas in considerable numbers. Each farmer received from the government a "quarter section," that is, a quarter of a square mile of land, or 160 acres. For a few years everyone was en thusiastic, and the land available for settlement was rapidly taken up.