The atmosphere of the earth, we now know, contains far more oxygen
or far less argon (whichever way one likes to put it) than does Mars.
The invigorating influences of this excess of oxygen upon the Martians
indisputably did much to counterbalance the increased weight of their
bodies.  And, in the second place, we all overlooked the fact that
such mechanical intelligence as the Martian possessed was quite able
to dispense with muscular exertion at a pinch.