Why should you place one hand under the base of the microscope as you carry it?

When moving your microscope, always carry it with both hands (Figure 1, at left). Grasp the arm with one hand and place the other hand under the base for support. Turn the revolving nosepiece so that the lowest power objective lens is "clicked" into position (This is also the shortest objective lens).

sound moves fastest in solids because the molecules are tightly packed and it allows sound to vibrate