Rocking a Three-Hundred Foot Masonry Tower 

 with Your Hand 



BY the mere pressure of your hand you can rock 

 "Sather Campanile" — the three-hundred-and-two- 

 foot memorial tower just completed on the campus 

 of the University of California. 



In order to minimize the danger from earthquake shocks, 

 the architect, Professor John Galen Howard, and the 

 engineer. Professor Charles Derlith, Jr., so built the strong 

 steel frame of the Campanile that cross-bracing is elimi- 

 nated at alternate stories. As a result the vibration of the 

 tower is like that of a steel rod one end of which is thrust 

 in the ground. In an earthquake the tower would vibrate 

 like a tree. 



According to Professor Elmer E. Hall's tests, the tower 

 has a vibration period of i .13 seconds. By pressing against 

 the steel frame at the top of the Campanile every 1.13 

 seconds he -as able to rock the tower, so that earthquake 

 recorders (seismographs they are called) registered the 

 vibrations. However, the amount of motion was less than 

 the thickness of this sheet of paper. 



The plan on which the tower was built is to prevent a re- 

 enforcement of the rocking caused by an earthquake vibra- 

 tion. For instance, a child can set a hammock swinging 

 violently simply by pushing at the right moment, no mat- 

 ter how hea\^- the load may be. If the pushes are not timed 

 correctly, the swinging is retarded. It is the same with the 

 Campanile. The plan is to prevent cumulative swaying, such 

 as would occur if the period of 

 the earthquake and the vibra- 

 tion of the tower were the same, 

 and such as would cause the 

 structure tocollapse. Mrs. Jane 

 K. Sather erected 

 the memorial 

 to her hus 

 band 



The pressure of 

 your hand will 

 swing the bell-tower 

 at Berkeley, Calif., 

 which in height is 

 second only to Wash- 

 ington Monument. It 

 was erected, as a memorial, 

 by Mrs. Jane K. Sather at 

 cost of two hundred and 

 twenty-five thousand dollars 



645 



