2l8 



THE POPULAR SCIENCE MONTHLY. 



household that desired is rarely above one horse, and generally under 

 it. A more complicated machine can, moreover, be used with success 

 in the workshop than in the household, as in the latter it would gen- 



FlG. 1. 



erally be in the care of attendants but little, if any, skilled in the use 

 of machinery. Certain general conditions are, however, common to 

 all. The work for which it is needed is generally of an intermittent 



