54 Dry- Docks How Used. 



propped up, the water is pumped out by steam, 

 and the dock, vessel and all, rise as you see in 

 the drawing. 



29. Some docks at low tide are entirely with- 

 out water. Such are enclosed by strong gates, 

 like those of canals, which keep the water in to 

 float the vessels. These also are dry-docks, al- 

 though not floating docks. 



30. When a vessel needs repairing or clean- 

 ing, it sails in with the rising tide, and is then 

 propped up. When the tide falls the gates are 

 opened, and the water passes out ; then the 

 gates are closed, and the water is kept out until 

 the vessel is ready to sail. These stationary 

 dry-docks are constructed only in those rivers 

 and bays in which the rise and fall of the tides 

 are sufficient for the purpose. 



31. The city of London, the largest city in the world, 

 has such docks ; its tides rise and fall about eighteen feet. 

 Such, also, are the magnificent docks of the city of Liver- 

 pool, where the tides rise and fall fifteen feet. Much of 

 that city's importance is due to these docks, in which can 

 be seen at any time steamships and other vessels from al- 

 most every country in the world, loading or unloading their 

 cargoes. The Brooklyn dry-dock is the finest in the 

 United States. 



32. How is a ship steered? By means of a helm, or 

 rudder. 



When sailors are far out at sea and no land is in sight, 

 what guides have they in ascertaining the directions ? The 

 stars and the mariner's compass. 



