PRESSURE 



EXPERIMENT 33. TO MEASURE THE WATER AND GAS 

 PRESSURE IN THE LABORATORY TABLES 



I. Attach a U-shaped tube to the water faucet by means 

 of rubber tubing, as shown in Figure 31, and then gently 

 turn on the faucet. Measure the 

 height ac, and the height be, and by 

 subtraction obtain the height of the 

 column ba. Since the pressure of 

 the water balances a column of mer- 

 cury ba inches in height, the pres- 

 sure of the water in pounds per 

 square inch is one half of ba. (See 

 "General Science," p. 93.) 



What is the pressure of the water in 

 your laboratory faucet ? 



Is the water pressure in the city con- 

 stant throughout the year ? When is it 



Measuring waler apt to be least ? 



2. In a similar way calculate the 

 gas pressure in your own laboratory 

 table. Which is under greater pressure, the water or the 

 gas? 



At what time of the day would the gas pressure be least ? 



FIG. 31. 



pressure in the labora- 

 tory. 



42 



