62 FIRST YEAR COURSE IN GENERAL SCIENCE 



one side of the balance than on the other, we have answered 

 the question. By repeating the same experiment in many 

 ways and under various conditions, we may arrive at certain 



conclusions which can 

 be summed up as a 

 definite law. 



In an elementary 

 course in science, we 

 cannot expect to dis- 

 cover any new laws or 

 even to prove any of 

 the old laws. All that 

 we can do is to satisfy 

 ourselves that these 

 great laws which others 

 have discovered hold 

 true as far as we have 

 the means to observe 

 them. 



The place where ex- 

 periments are made is 

 called a laboratory. 

 The word means " work- 

 shop." 



63. Apparatus. The 

 things with which we 

 work, such as balances, 

 rulers, thermometers, 

 microscopes, gas 

 burners, and glass 

 tubes, are called pieces 



FIG. 24. A COMBINATION OF SIMPLE 

 MACHINES 



This rotary crane is such as is used in 

 unloading ships, and in constructing dams, 

 bridges, and great buildings. It shows a 

 combination of a lever, pulleys, and wheel 

 and axle. The lever, called the jib, is 

 fastened at one end to an upright post, with 

 which it rotates, so that the load it supports 

 can, after being lifted, be deposited else- 

 where. The cable, which supports and lifts, 

 runs over pulleys and is wound up on the 

 drum of a wheel and axle. How much will 

 the load rise if the cable is wound once 



around a drum 2 ft. in diameter? 



of apparatus. They 



should be handled with care, kept in good order, and re- 

 turned to their proper places. 



The weight of a body is determined by the use of a piece 



