104 SMALL WATER SUPPLIES. 



Continuous Running. This expression is frequently 

 made use of without qualification ; or the engine is 

 said to be required to run "day and night," without 

 any period being assigned, which is obviously 

 absurd. When an engine is required for long runs 

 be careful always to state how many hours it is to 

 work without stopping, and how long the stop is 

 to be. 



Height above Sea-level. A gas or oil engine gives 

 off less power as its position is elevated, owing to 

 the diminished atmospheric pressure and consequent 

 lessened supply of oxygen. At moderate heights 

 the loss is inappreciable, but at considerable altitudes 

 it becomes serious. Roughly speaking, the loss of 

 power may be taken as about 3 per cent for each 

 thousand feet above sea-level. When, therefore, 

 there is any question of placing an engine at any 

 considerable elevation, the actual height should be 

 stated, in order that the proper size be selected, and 

 the necessary adjustments made. 



Cleanliness. A gas or oil engine invariably works 

 better if kept clean free from grit and dust. A 

 clean engine and engine-room indicate that the 

 engine is being properly cared for. A dirty engine 

 implies neglect not only of cleaning but of most of 

 the minor duties to which a caretaker ought to give 

 his attention. A dirty, and therefore neglected, 

 engine may involve trouble from hot bearings, pre- 

 mature ignition, and other causes. A close adher- 

 ence to the " Instructions " issued with each engine 

 will well repay the small trouble involved. In cer- 

 tain trades where a large quantity of dust cannot be 

 avoided, the engine should be placed in a well-sealed 



