In this machine there is a linkage for central symmetry with centre on O, so that the points P and Q are corresponding, and also a linkage for a central symmetry with centre on R, and the linkages are pivoted on Q so that Q and T are corresponding, and P and Q are corresponding in the product of the two central symmetries.Also a traslator (of Kempe) connect the points P and T. As a result , it is possible to give a mechanical proof that the product of two central symmetries is a traslation.