HUMBOLDT RIVER 



2870 



HUMMING BIRD 



the king of Prussia asked him to live in Ber- 

 lin, so from that time his home was in that 

 city; a portion of the time he resided at the 

 court. The year he moved to Berlin he 

 delivered a remarkable series of lectures which 

 formed the basis for his Cosmos, wherein he 

 described nearly all that is now known of 

 the physical universe. His entire life was spent 

 making experiments which have added a vast 

 fund of knowledge to the scientific world. 



Consult Stoddard's Life,, Travels and Books of 

 Alexander Humboldt. 



HUMBOLDT RIVER, the longest river of 

 Nevada, rises in Elko County, in the north- 

 eastern part of the state and flows southwest- 

 erly for about 350 miles into Humboldt Lake, 

 in Churchill County. Its course is through a 

 barren region whose soil is chiefly alkaline, and 

 its waters are so saturated with alkali that they 

 are salty. The Humboldt is only a few yards 

 wide, and towards its mouth it grows even 

 smaller through evaporation. Along the sides 

 of its valley are rugged mountain peaks. This 

 valley, which is traversed by the Southern 

 Pacific' Railroad, is the only pass extending 

 east and west through the mountains of Ne- 

 vada. 



HUME, DAVID (1711-1776), author of the 

 more important principles of modern political 

 economy, and a historian of note. Hume also 

 influenced, to a great degree, the philosophic 

 thought of the eighteenth century. He was 

 born in Edinburgh, the younger son of the laird 

 of Ninewells in Berwickshire. His first work, 

 published partly in 1739 and partly in 1740, was 

 the Treatise upon Human Nature, which was 

 a valuable contribution to the science of psy- 

 chology. Hume taught that one could not 

 have ideas or thoughts except such as were 

 derived from impressions gained through the 

 several senses, either directly or by means of 

 memory images. 



In 1741 appeared Essays, Moral, Political 

 and Literary, his next work. Before Hume's 

 advent as an historian Great Britain did not 

 recognize history as a branch of polite litera- 

 ture. Hume believed that history should not 

 be a mere compilation of dates and facts or 

 a record of war and intrigue. He included in 

 his histories the literature, the conditions of 

 life and the manners of the people. He was 

 the first Scotchman to devote his entire time, 

 and with marked success, to literature. 



HUMIDITY, humid'iti. As the moisture 

 from the seas, rivers and lakes evaporates it 

 fills the air with water vapor, a condition of 



the atmosphere which is described by the term 

 humidity. When the air contains a great deal 

 of vapor and feels damp, the humidity is said 

 to be high, but if very little moisture is present 

 the humidity is low. Usually the air is not 

 completely filled with water vapor, unless it 

 is raining, but the amount varies greatly with 

 the temperature and location. The higher the 

 temperature of the air, the greater the amount 

 of vapor it may contain. When as much 

 moisture is present as the atmosphere can hold 

 at a certain temperature, the air is said to be 

 saturated, or at the dew-point. The lower air 

 over the ocean is usually almost saturated, 

 while far inland in desert regions the air is so 

 very dry that a person is not seriously affected 

 by either extreme heat or cold. 



The ratio of the amount of water vapor in 

 the air to the amount required for saturation 

 at that temperature is called the relative hu- 

 midity. Thus, if the air contains one-half the 

 amount of vapor which it can hold the relative 

 humidity is fifty per cent. Wherever the land 

 is agriculturally productive without irrigation, 

 the relative humidity is about sixty-five per 

 cent. A person feels "sticky" and uncomfort- 

 able when the humidity is too high, for the 

 perspiration of the skin does not evaporate 

 easily; but on the other hand too little hu- 

 midity is injurious to the health. For this 

 reason some means should be adopted for 

 getting vapor into the atmosphere in a heated 

 living room. Basins of water may be kept on 

 registers, a jet of steam may be allowed to es- 

 cape from a radiator, or a water pan may be 

 kept in a furnace. The amount of moisture in 

 the air is determined in various ways, but gen- 

 erally a form of hygrometer, consisting of two 

 thermometers, is used. W.A.E. 



Related Subjects. The reader is referred to 

 the following articles in these volumes : 



Cloud 

 Evaporation 



Fog 

 Rain 



HUM 'MING BIRD, a family of birds found 

 only on the American continents, and of special 

 interest because of their small size, brilliant 

 plumage and their rapid, darting flight. These 

 tiny birds have been named with reference to 

 the whirring sound made by their wings. Of 

 more than four hundred species which have 

 been recognized, only eighteen are known in 

 the United States; of this group, all but one 

 species belong to the Southwestern and Pa- 

 cific coast states. The smallest of the humming 

 birds, when stripped of their feathers, are no 

 larger than a bumblebee, and only a few are 



