  William Thomson proved Carnot's theorem basing on postulate: "It is
impossible, by means of inanimate material agency, to derive mechanical effect
from any portion of matter by cooling it below the temperature of the coldest
of the surrounding objects". The present paper demonstrates that Carnot's
theorem can be proved based on the contrary Thomson's postulate: "It is
impossible to use the mechanical effect to the heating the coldest of
surrounding objects". A conclusion that Carnot's theorem does not follow from
the Thomson's postulate has been drawn.
