Final answer:
The change in elevation of the mercury can be determined by observing the difference in the heights of the mercury column in a U-tube.
Step-by-step explanation:
The change in elevation of the mercury can be determined by observing the difference in the heights of the mercury column in a U-tube. The height difference is the change in elevation. For example, if the height on the left side is higher than the right side by 4.63 inches, then the change in elevation of the mercury is 4.63 inches.