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thirty-nine inches long, the length counted from the point where the 

 thread is attached to the center of the weight. Have the pupils deter- 

 mine how many times in a minute this pendulum vibrates. If it does 

 not vibrate sixty times in a minute correct the length till this is its rate. 

 Keep this pendulum as the time keeper for the succeeding experi- 

 ments. 



Have them make other pendulums of the same length, some with 

 much heavier weights and some with lighter weights and determine if 

 there are differences in the rate. 



Have the pupils construct a pendulum long enough to vibrate once in 

 two seconds, and one short enough to vibrate twice in a second. Let 

 them measure and compare these with the seconds pendulum. Do the 

 same for pendulums vibrating once in three seconds and three times in 

 a second. A high ceiling, a window or a tree will give an opportunity 

 for hanging a long pendulum. 



The use of the pendulum as a time instrument can now be explained. 

 The importance of accurate and uniform time in business and in rail- 

 road and other travel, etc., etc., may be seen. On Mt. Hamilton every 

 day at noon a pendulum in a fine clock stationed there, is connected by 

 electric wires with most Western Union Telegraph Offices on the Pacific 

 Coast. In any one of these offices at noon anyone can hear the tele- 

 graph instrument beating in unison with the pendulum on Mt. Hamil- 

 ton. Thus all time pieces might be kept in accurate accord with this 

 one. 



In other parts of the United States are centers from which the time is 

 sent out in the same way over all that region. 



The story of the discovery of the properties of the pendulum and the 

 effect of its application to time-keeping could be made interesting and 

 profitable. (See Encyclopedia, etc.) 



Note the relation of the pendulum to falling bodies; the effect on the 

 pendulum if the earth were heavier or lighter; if the pendulum were 

 near or father away from the center of the earth, might be taken up in 

 some of the grades under certain conditions, but would perhaps bet- 

 ter be deferred at present. 



Silk Worm Moths. 



When a good supply of mulberry leaves can be obtained, silk worm 

 moths offer excellent opportunities for observing with small trouble the 

 whole cycle of the life of this group of insects. 



If some of the eggs be obtained and placed in some convenient place 

 in a warm room, they will in a few days hatch out into very small cater- 

 pillars. These should be immediately fed with fresh mulberry leaves. 

 They will feed voraciously on the leaves, never leaving the place where 

 they are kept if the supply of leaves is kept up. After feeding and 

 growing for some time they come to a period • in which they are ready 



