Sea-Sickness symptoms are experienced by many persons when they are subjected to the pitching and rolling motion of a vessel at sea.
Plutarch was, perhaps, the first theorist on the subject. He thought that sea-sickness was caused by the smell of the salt-water; and, following him, men have propounded theory after theory, only to leave us of today with a large stock of theories, and but few good results to show for them.
This book deals with the cause of Sea-Sickness and the vertigo.

"In learning to walk we judge of the distances of the objects, which we approach, by the eye; and by observing their perpendicularity determine our own. This circumstance not having been attended to by the writers on vision, the disease called vertigo or dizziness has been little understood. When any person loses the power of muscular action, whether he is erect or in a sitting posture, he sinks down upon the ground; as is seen in fainting fits, and other instances of great debility. Hence it follows, that some exertion of muscular power is necessary to preserve our perpendicular attitude. This is performed by proportionally exerting the antagonist muscles of the trunk, neck, and limbs; and if at any time in our locomotions we find ourselves inclining to one side, we either restore our equilibrium by the efforts of the muscles on the other side, or by moving one of our feet extend the base, which we rest upon, to the new center of gravity..."