146 PHYSICAL GEOGRAPHY. 



Besides these favoring conditions the soil is principally Loess and 

 Modified Drift and contains from sixty to eighty per cent, of sili- 

 cious matter, very finely comminuted, which readily permits all 

 \vater from rains and snows to percolate through it. Beneath the 

 Loess unmodified Drift occurs, and this being made up of sand, 

 pebbles and boulders, all the conditions for complete drainage are 

 completely supplied. Even the black, rich surface soil, so wonder- 

 ful for its fertility, contains silicious material in sufficient quantities 

 to produce good drainage. The consequence of such inclination of 

 the land and character of the soil and subsoil is that over large 

 areas in the State standing water is unknown. Indeed, many 

 citizens of the State, who have not traveled much, fancy that there 

 is no standing water within its boundaries. There are, however, a 

 few limited localities where swamps and bogs exist, such as a por- 

 tion of the Missouri bottom in Dixon and Burt counties, and on 

 small portions of the level prairies, in Clay, Webster, Fillmore and 

 Saline counties. Even here the general elevation of these counties, 

 and the constant movement of the winds seems to counteract 

 the conditions of the surface that favor malarial diseases. Not 

 only does the atmosphere seem to be constantly in motion, but is 

 also comparatively dry. In summer and autumn the prevailing- 

 winds are south and southwest. In winter the prevailing winds 

 are from the north and northwest. In spring the winds, as else- 

 where, are exceedingly variable, and seem to be nearly equally 

 divided, between north and northwest, and south and southwest. 

 Often in the spring the prevailing winds are from the northeast. 

 The air is always remarkably pure and generally clear. All these 

 are conditions that are unfavorable to- the production and propaga- 

 tion of miasmatic poisons. 



An additional reason for the healthfulness of Nebraska might be 

 the presence of an unusual quantity of ozone in the atmosphere. 

 I merely suggest this as a partial explanation of this fact, as no 

 single cause, but many combined, produce the healthfulness of a 

 region. In the section on the Atmosplierc of Nebraska, I have 

 shown that the atmosphere of Nebraska is exceptionally full 

 of ozone, caused probably by its highly electric condition, and the 

 constant movement of electricity through dry air. As is well 

 known, ozone is found in the east in perceptible quantities only 

 after thunder storms, by which many suppose it to be produced. 

 As here during much of the time, before as well as after thundci 



