Show why bowlers break banks there anro very few bridges in the world over which troops are allowed to marchin regular step in general when coming to a bridge particularly suspension bridge the drums or hands are stopped the array is broken and the soldiers pass over without keeping step or brather pains not to keep step the reason is found in the tact that a very blight initial vibration if continued ia imparted to the whole structure and in a short time becomes so strong a downward strain at every recurrence as speedily to endanger the safety of the strongest bridge the same principle is illustrated in i some bouses which can bo made to r tremble from roofie foundation by per and regularly pressing with the foot on a loose board in one of the floors A curious circumstance is been in the case of certain churches in which it is dangerous to heavy pedal pipes of a grand brgan for the reason that the vibration becomes so great as to Ss hatter the panes i of glass in dows and imperil the safety of aba roof st LOTUS globo M |