LABOR IN CHAINS
by Diego Rivera

"This picture reflects and enlarges the signs of enslavement and oppression in the corresponding panel (panel V) on the opposing wall. There Thoreau was in jail, here Tom Mooney looks through the grating of his cell. There a Negro was being whipped, another shot, and a third in stocks; here the nine Scottsboro boys are in prison, a worker in shackles is being lashed, Sacco and Vanzetti are seated in the electric chair, and the Statue of  Liberty itself is seen through the prison bars. There slaves are seen in  chains and iron collars; here 'free' workers are handcuffed to the machines at which they labor. The handcuffs are no mere painter's symbolism, but a faithful copy of a highly efficient modern punch press which is worked by manacled workers whose hands are automatically pulled back by the handcuffs every time the punch press descends. This prevents mashing of the hands by the press, a costly interruption of the work, and at the same time automatically regulates the speed of the hands so that no matter how tired the worker may become, the handcuffs guarantee the same invariant rhythm--in the case of this particular machine, over 1,000 punches an hour. The advertising literature which provided Rivera's 'model' boasted that the machine would yield '12,000 punches in a 9-hour day--as many punches per hour in the last hour as in the first.'"

- Bertram Wolfe, in Portrait of America, by Diego Rivera.