30 



INTRODUCTION. 



3uch quantities as to produce very perceptible effects upon the animal system, or to show 

 decided chemical powers in other ways, the spring becomes a mineral water ; if the tempera- 

 ture of the water is above the ordinary temperature, then we have thermal or warm springs. 

 Mineral waters maybe, 1. acidulous; 2. chalybeate; 3. sulphureous; 4. saline. The first 

 generally owe their sparkling appearance and acid qualities to fixed air or cp-'-'s.onic acid. Such 

 are the waters of Tunbridge, In England, of Pyrmont, Spa, and Selteis, in Europe, and 

 others. The chalybeates generally contain several grains of oxide of iron, mixed with other 

 salts , of this class are the Harrowgate springs, in England, the celebrated springs of Saratoga 

 and Ballston, in New York, and many others in this country. Sulphureous waters owe their 

 qualities to the presence of sulphuretted hydrogen, and some salts in which sulphuric acid is 

 combined (sulphates) ; such are the fine group of sulphur springs in Western Virginia, and the 

 waters of Aix-la-Chapelle, m Europe. Saline waters contain large quantities of different salts, 

 such as common salt, Epsom, Glauber's salt, &c. Those which have but a small portion of 

 itie medicinal salts, are used for the manufacture of common salt, as in New York, Western 

 Virginia, Pennsylvania, and all over the Western States. The source of the peculiar impreg- 

 nation of these various waters, is the mineral beds through which they flow. The temperature 

 of thermal waters varies from 50^ or 60^ to boiling point ; the Hot Springs of Virginia are 

 about 106°, those of Arkansas nearly 200°, and the Geysers of Iceland 212°, or at boiling 

 point. Thermal waters are sometimes pure, and sometimes contain mineral ingredients. In 

 some cases carburetted or sulphuretted hydrogen issues from the ground in great quantities, 

 forming blotcing or burning springs. The village of Fredonia, in New York, is lighted by 

 natural gas, supplied in this manner. 



8. Rivers. Rivers are natural drains, which convey to the sea that portion of the waters 

 falling upon the earth, which does not pass oil" by evaporation, or go to nourish organic bodies. 

 The sources of rivers are generally springs, or small streams, fed by the melting of snow and 

 ice upon the mountains, or by rains. 



9. Basin. The district from which the waters of a river are derived, )s called its basin. 

 The basin is bounded by highlands, which are sometimes mountainous, and which divide It 

 from other basins. The water descending from the water-shed or dividing ridge collects into 

 brooks, the brooks unite into rivulets ; the rivulets united form the main trunk or river, which 

 conveys the waters of the whole to the sea. All these descend over inclined planes, so that 

 the lowest point of each brook is that where it joins the rivulet ; the lowest point of the rivulet 

 that where it unites with the main streai^.i ; and the lowest point in the whole system that where 

 the river falls into the sea. These basins form important natural divisions. Those streams 

 which empty themselves into larger streams are called the tributaries of the latter. 



The following table shows the length of some of the principal rivers. . . 







Principal 



Rivers of JS^orth Jlmerica. 







Kamcs. 



Length. 



JVames. 



Lens'th. 



JVames. 



Length. 



JSarnes. 



Length. 



Missouri 



4,400 



Del Norte 



2,000 



Ohio 



1,350 



Savannah 



600 



Mississippi 



3.000 



Nelson 



1,500 



Kansas 



1,200 



Potomac 



550 



Arkansas 



2,100 



Columbia 



1,500 



White River 



1,200 



Connecticut 



410 



St. Lawrence 



2,000 



Red River 



] ,500 



Tennessee 



1.100 



Hudson 



324 



Mackenzie 



2,000 



Platte 



1,500 



Alabama 



650 



Delaware 



300 







Principal 



Rivers in South America. 







Karnes. 



Length. 



A''ames. 



Length. 



Xamcs. 



Length. 



Karnes. 



Length. 



Maranor 



4,500 



Orinoco 



1,800 



St. Francisco 



1,500 



Xingu 



1,400 



La Plata 



3,000 



Tocantins 



1 ,800 



Paraguay 



1,400 



Topajos 



1,300 



Madeira 



2,500 



Ucayale 



1,600 









Principal Rivers in Europe. 









J^ames. 



Length. 



IVamcs. 



Length. 



Karnes. 



Length. . 



A''ames. 



Length 



Volga 



2,040 



Rliine 



670 



Tagus 



580 



Guadiana 



420 



Danube 



1,710 



Elbe 



570 



Dwina 



480 



Rhone 



390 



Don 



1,080 



Loire 



540 



Oder 



450 



Pruth 



- 390 



Dnieper 



1 ,(i50 



Vistula 



500 



Niemen 



450 



Po 



375 



Kt'ini 



780 



Dniester 



480 



Dwina, o Duna 



480 



Ebro 



376 



