If it be true, as Dr. Carpenter asserts, that in the case of the general oceanic circulation advocated by him “viscosity” simply _retards_ motion, but does not _prevent_ it, I certainly agree with him “that the constantly maintained difference of gravity between the polar and equatorial columns really acts as a _vis viva_ in maintaining a circulation between them.” But to assert that it merely retards, but does not prevent, motion, is simply _begging the question at issue_. It is an established principle that if the _force_ resisting motion be greater than the force tending to produce it, then no motion can take place and no work can be performed. The experiments of M. Dubuat prove that the _force_ of the molecular resistance of water to motion is _greater_ than the _force_ derived from a slope of 1 in 1,000,000; and therefore it is simply begging the question at issue to assert that it is _less_. The experiments of MM. Barlow, Rainey, and others, to which he alludes, are scarcely worthy of consideration in relation to the present question, because we know nothing whatever regarding the actual amount of force producing motion of the water in these experiments, further than that it must have been enormously greater than that derived from a slope of 1 in 1,000,000. _Supposed Argument from the Tides._—Dr. Carpenter advances Mr. Ferrel’s argument in regard to the tides. The power of the moon to disturb the earth’s water, he asserts, is, according to Herschel, only 1/11,400,000th part of gravity, and that of the sun not over 1/25,736,400th part of gravity; yet the moon’s attractive force, even when counteracted by the sun, will produce a rise of the ocean. But as the disturbance of gravity produced by difference of temperature is far greater than the above, it ought to produce circulation.