  Lord Kelvin's postulate is a standard form of statement of the second law of
thermodynamics. Caratheodory's principle is also considered as a different form
of this law. Landsberg deduced Caratheodory's principle from Kelvin's postulate
and Dunning-Davies deduced its converse to show the equivalence of the two
principles, and these deductions remained forerunners for later works. Here we
show that these deductions are flawed and therefore, invalid. The fallacies in
these works arose due to the fact that these authors had taken an inadmissible
form of statement of Kevin's postulate and had considered an inappropriate
cyclic process, for their deductions. The equivalence between Caratheodory's
principle and Kelvin's principle of the second law, therefore, remains
unproved.
