g96 



SEASICKNESS. 



vnthdrawii. 



js in all cases vefened directly to the stomach, which ia 



seized with such instantaneous retching, that no person who 



has not been so siiuaie, can form a just conception of it*. 



Tendency to Jn thus referring the sensations of seasickness, in so great 



faint from the , i_ • , t i- i 



pressureon the ^ degvee, to the agency ot mere mechanical pressure, I teel 



brain being confirmed by considering the consequence of an opposite 

 motion, which, by too quickly withdrawing blood from the 

 head, occasions a tendency to faint, or that approach to 

 fainting, which amounts to a momentary giddiness with di- 

 minution of muscular power. At a time when 1 was much 

 fatigued by exercise, I had occasion to run to some distance, 

 and seat myself under a low wall for shelter from a very 

 heavy shower. In arising suddenly from this position I was 

 attacked with such a degree of giddiness, that I involuntarily 

 dropped into my former postijre, and was instantaneouslj' 

 relieved, by return of blood to the head, from every sensa- 

 tion of unea&iness. 



Since that time, the same affection has frequently oc- 

 curred to me in slighter degrees, and I have observed, that 

 it has always been under similar circumstances of rising 

 suddenly from an inclined position, after some degree of 

 previous fatigue. Sinking down again immediately removes 

 the giddiness ; and then, by rising a second time more gra- 

 dually, the same sensation is avoided. 



iiarthquakes * There is pne occasion, upon which a slighter gensation of tMs kind 

 ^ffeot the sto- is perceived, and it appears to indicate the direction of the motion from 

 mach. wliich it arises, to be downwards. " In a country subject to frequent 



returns of earthquakes," it is said * " a few minutes before any shock 

 came, many people could foretel it by an alteration in their stomachs ; 

 an effect which" (it is added) " always accompanies <he wavt-ike 

 motion of earthquakes, when it is so weak as to he uncertainly dis- 

 tinguishable." (l^Iiehell, Phil. Trans, vol. LI, 6l0.) 



It seems, that the vapours to which these tremendous concussions 

 are owing, immense in quantity, and of prodigious force, being for a 

 time confined on all sides, elevate the surface of a country to a vast 

 extent, until they cither find vent, or meet with some partial cause of 

 tpndensation ; and hence the alternate heaving and subsidence of the 

 gioiind will produce much the same effects as the rising and falling of 

 the swell at sea. 



* Phil, Trans. v6l. XLII, p, 41. 



PAi^r III 



