AIRSHIP 1 



valve which allows air to escape from the tube 

 t, and in the piston is another valve which 

 allows air in the cylinder to escape into the 

 space above the piston. 



Raising and lowering the pump-handle has 

 an immediate effect. A down-stroke of the pis- 

 ton closes the valve in the base of the cylinder. 

 The expansive force of the air confined below 

 the piston head opens the valve in the piston, 

 and some of the air escapes to the upper side of 

 the piston. The next up-stroke of the piston 

 closes the cylinder valve, and opens the one in 



CROSS-SECTION OF AIR PUMP 



the piston. The air which escapes through the 

 piston valve into the space above the piston is 

 forced out through an opening in the top of the 

 cylinder when the piston moves upward. The 

 expansive tendency of the air in the receiver r 

 again fills the lower part of the cylinder, and 

 the entire process is then repeated until a par- 

 tial vacuum is created. A perfect vacuum cannot 

 be obtained by this apparatus because of me- 

 chanical imperfections which are unavoidable. 

 But for ordinary experiments the vacuum is so 

 nearly perfect as to cause no difficulties. C.R.M. 



AIRSHIP. See FLYING MACHINE. 



AISNE, ane, a river in the northeastern part 

 of France, which henceforth will be one of the 

 historic streams of Europe. Rising in the Ar- 

 dennes mountains it flows first north and then 

 almost straight west and joins the Oise River 

 near Compiegne. Its length is about 180 miles, 

 of which nearly 100 miles are -navigable. Hhe 

 river Aisne has nearly a parallel course with 

 another historic river, the Marne, (which see), 

 that flows a little distance to the south of it. 



Battle of the Aisne. During the War of 

 the Nations two very important battles were 

 fought on its banks. The first, known as the 

 Battle of the Aisne, took place in September, 

 1914. After the Germans were defeated on the 

 Marne, they retreated across the Aisne and 

 took up positions prepared beforehand. The 

 French and English pursued them, and a series 

 of desperate battles with great losses on both 



AIX-LA-CHAPPELLE 



sides took place. No decisive victory was won 

 by either side, and the opposing armies main- 

 tained their positions and began to dig them- 

 selves into a series of fortified trenches. It was 

 after the battle of the Aisne that trench war- 

 fare started, which became such a character- 

 istic feature of the War of the Nations. 



The second battle on the Aisne took place in 

 January, 1915. It began with a great offensive 

 movement by the French, who succeeded in 

 crossing the river at Soissons. They occupied 

 some ground held by the Germans, but after 

 desperate battles lasting five days they were 

 compelled to retire across the river to their old 

 positions. See WAR OF THE NATIONS. 



AIX, ayks, a city of France, in the depart- 

 ment of Botiches-du-Rhone, eighteen miles by 

 rail north of Marseilles. It contains the facul- 

 ties of letters and law of the University of Aix- 

 Marseilles, and for this reason some quarters of 

 the town have the aspect of the famous Latin 

 Quarter of Paris. Aix is the seat of a Roman 

 Catholic archbishop, and it has an interesting 

 cathedral in Gothic style, dating from the 

 twelfth century. There are here a number of 

 warm springs, containing lime and carbonic 

 acid, which have been used since the Roman 

 period. 



Aix was founded in 123 B. c. by the Romans, 

 who named it Aquae Sextiae. It was near this 

 place that Marius gained in 102 B. c. his famous 

 victory against the Cimbri and Teutons. Dur- 

 ing the Middle Ages Aix was the capital of an 

 independent county of Provence and became 

 an important seat of learning and a brilliant 

 artistic center. The town began to lose its im- 

 portance when Provence was passed under the 

 crown of the kings of France in 1487. 



AIX-LA-CHAPELLE, ayx lah sha pel' , since 

 1815 officially but not popularly known as 

 AACHEN, is a city of Rhenish Prussia, 44 miles 

 southwest of Cologne. The most important 

 building is the cathedral, the oldest portion of 

 which was erected in the time of Charlemagne, 

 as the palace chapel, about 796. This place 

 was the favorite residence of Charlemagne, who 

 died in 814, and was here buried. A gold coffin 

 in the cathedral contains his .remains. Thirty- 

 seven German emperors and eleven empresses 

 have been crowned in the city, and the imperial 

 insignia were preserved here till 1795, when 

 they were carried to Berlin and placed in the 

 imperial treasury. 



There are a number of warm sulphur springs 

 in and near the city, one having a temperature 

 of 140, and several mineral springs which have 



