NATURE-STUDY LESSONS. 191 



l6. (a) About 9 p.m. in the first week of September, 



three bright stars may be seen overhead 



fprmi-ng a large triangle. The north-west 



GB& is called Vega, the north-east one 



Dfijieb, a.,nd the so.uth one Altair. They 



are in three different constellations called 



respectively the Harp, the Swan and the 



Eagle. Compare the color of Vega with 



that of the other two stars. 



(J)) Make a map showing the. relative position of 



these three and the North Star. 



Some other constellations that are referred to in literature and are easily 

 learned are the Northern Crown, which is overhead at lo p. m. in the 

 middle of June, the Lion, overhead in the middle of April at 9 p.m., 

 " The Heavenly Twins " and the Dog Star, about 9 p.m. in the middle of 

 February, the Great Square of Pegasus, at 9 p. m. in the beginning of 

 November, and the Smaller Bear or Little Dipper of which the North Star 

 forms the end of the handle. 



LIX.-THE LEVER AND FULCRUM. 

 A. Apparatus :— 



{a) A stout pry, with a triangular block to serve as 



a rest. 

 {b) A flat ruler twelve inches long, 

 (f) A number of equal weights. 



1. {a) Try to raise, the teacher's desk, or a cupboard, 



or any other heavy object by lifting it with 



the hands alone. 



{b) Next raise it by using the pry. 



{c) What difference is observed ? 



A ruler, handspike or crowbar used to raise heavy bodies is called a 

 lever. The support on which the lever rests and about which it turns is 

 the fulcrum. The body raised is the weight, and the force applied to 

 raise the weight is the power. 



2. In raising the desk, where is the fulcrum with 

 reference to the weight and the pow'er? " 



