From the July 5, 1930, issue

POWER PLANT SENTINELS

When hundreds of thousands of horsepower traveling with the speed of lightning are instantly halted, you may be sure there will be a grand disturbance. And there is, but all the fuss is confined in steel tanks 25 feet tall and 10 feet wide, filled with oil.

Two such tanks are shown on the front cover of this week’s SCIENCE NEWS-LETTER.