AMPHIBIANS 



AMSTERDAM 



visible, and the only way to measure it is by 

 what it does. If a current of electricity is 

 passed through a solution which contains a 

 metal, the electricity decomposes the solution 

 and deposits the metal as a solid. This process 



ctrolysis, and the unit of strength of the 

 electric current is the ampere. A current with 

 a strength of one ampere will deposit, under 

 normal conditions, 0.001118 grammes of silver 

 or 0.0003287 grammes of copper in one second. 

 By Ohm's Law the strength of a current is the 

 initial force divided by the resistance it over- 

 comes in doing its work; expressed in quanti- 



amperes equal volts divided by ohms. 

 Thus the ampere is the unit of any electric cur- 

 rent, no matter for what purpose it may be 

 used. The instrument for measuring the num- 

 ber of amperes is really an ampere-meter, com- 

 monly shortened to ammeter. It is really a 

 form of galvanometer (see GALVANOMETER). 

 The reader is advised to read the articles 

 ELECTRICITY, ELECTROLYSIS and OHM'S LAW be- 

 fore making any further attempt to study the 

 ;ls of this subject. 



The ampere is named in honor of Andre 

 Marie Ampere (1775-1836), a great French 

 physicist, who proved the identity of magnet- 

 ism and electricity and investigated the sub- 

 ject of electric currents. He first stated two 

 simple laws which form the basis of modern 

 electrical practice: (1) two parallel currents 

 having the same direction attract each other; 

 (2) two parallel currents having opposite di- 

 rections repel each other. He also invented a 

 form of needle which made possible the gal- 

 vanometer. 



AMPHIBIANS, am fib' earn, a group of 

 creeping or leaping, cold-blooded animals which 

 hatch from eggs and breathe at first by means 

 of gills, and afterwards partly or wholly by 

 means of lungs. Amphibian is from a Greek 

 word meaning having a double life, and is 

 given to these animals because they can live 

 both on the land and in water. In all stages of 

 growth, however, it is necessary that they have 

 moisture. 



\nipliibians are divided into two classes: 

 th' tailless, containing toads and frogs, and the 



i, containing newts and salamanders. The 

 eggs are laid in fresh water streams and ponds, 

 and the young are called tadpoles. Amphibians 

 belong to that class of animals having a back- 



. tin whole class being called vertebrates. 

 Tlu> v...:.l means backboned animals. 



Topi-n Tor a detailed description of 

 important members of this order, as 



well as for illustrative material, consult the fol- 

 lowing articles : 



Bullfrog Salamander 



Frog Tadpole 



Horned Toad Toad 



Mud Puppy Tree Frog 



Newt 



AMPUTATION, am pu ta' shun, in surgery, is 

 the separation of a limb or other part from the 

 body. If an arm or a leg is to be amputated 

 the bone must first be laid bare by a deep rut 

 in the flesh. This cut should be made in a slant- 

 ing direction, so as to leave one or more flaps 

 of flesh. The ends of the blood vessels must be 

 tied, to prevent bleeding to death, and then 

 when the bone has been sawed off the flaps may 

 be held smoothly over the stump and stitched 

 in place. Amputation is usually necessary in 

 case of severe accidents or malignant growths, 

 and always in case of gangrene poisoning. The 

 advance of medical science, however, has made 

 it possible in many cases to save a leg or arm 

 which, under similar conditions a century ago, 

 would have been removed without hesitation. 



Amputation, while recognized as a serious 

 operation, is seldom dangerous to life. It has 

 been practised from very early times, but al- 

 most until our own days the percentage of 

 deaths from bleeding or blood-poisoning was 

 very large. It was in the seventeenth century 

 that surgeons learned how to stop bleeding by 

 the use of ligatures and tourniquets, but it was 

 not until the nineteenth century that they 

 learned how to prevent infection. See SUR- 

 GERY. 



AMSTERDAM, am' stur dam, Holland's me- 

 tropolis and one of the chief commercial cities 

 of Europe, famous for its art treasures and as 

 the center of the diamond cutting industry of 

 the world. The name means the dam of the 

 Ansl t l. thr river which flows through tin- city. 

 On account of thr lowness of its site, the 

 greater part is built on piles and it is divided 

 into about ninety islands by numerous canals 

 crossed by nearly .W) bridges. Tin- harbor, 

 formed by the Y or Ij, an arm of the Zuyder 

 lies along the whole north side of the city 

 and is surrounded by various docks and basins. 

 A ship canal fifteen miles long and twenty-two 

 to twenty-six feet deep connects the Y with the 

 North Sea, and the city is joined to Helder, 

 commanding the entrance to the Zuyder Zee, 

 he North Holland Canal, forty-six miles in 

 length. 



Among the principal buildings in Amsterdam 

 are the palace, originally built as a town hall, 

 the Stadthuis, the Bourse, the Rijks Museum or 



