0^ TilT ART or SWIMMING. 



327 



"action is afterwards used in swimming to support your head 

 " higher above water, or to go forward through it." page 474. 



The Doctor proceeds to tnake several observations on the Dr. Franklin's 

 natural tendency of the human body to float in the water; at t'^.lZltm^^ ""'^ 

 the same time that he advises his friend not to trdst to the chance floatage of the 

 that he Inay have presenfce of mind sufficient to take advantage ^"™^" ^'^^^' 

 of those hints in a case of real danger, but to learn to swim. 

 The substance of these remarks is : 1st. — That the limbsand head 

 of an human body are heavier than fresh water ; but the trunk 

 is lighter, merely because the lungs are inflated. 2d. — That the 

 head is heavier than sea water; but the limbs and trunk are 

 lighter. 3d. — That a person throwing himself on his back in 

 sea water, will float with his face clear, so as to breathe with 

 ease. 4th. — That in fresh water the legs will gradually sink, 

 and the body will float in an erect posture. 5th. — That, in 

 this posture, if the head be held in its natural position, the 

 surface of the water will reach higher than the nostrils, and 

 perhaps a little above the eyes.* 6th. — That if the head be 

 leaned quite back, the nos& and mouth will be always above 

 the water and free for breathing, and the body will rise and fall 

 on every such inspiration and expiration. 



I am rather surprized at the Doctor's direction about the The Doctor 

 egg, and the eyes open underwater; because it seems as i^su^nos^thT 

 he thought the submerged experimentalist could see the egg. man can see 

 I know several respectable persons who affirm that they can j'^^g jg^con- 

 see objects under water ; but as long as we are assured that trary to optical 

 distinct vision requires that light shoul dcome to a focus on the ^*^'^''^^®» 

 retina, and that a very considerable part of the refraction per- 

 formed by the eye is effected at the c(mvex surface of the 

 cornea, intercedent between that substance and the air, we must 

 refuse our credit to sucli assertions. Besides which, experi- 

 ment will easily clear up the matter to those who know nothing 

 of optics. For every one may prove by trial, with a bason or 

 tub, that vision under water is scarcely more distinct than that 

 which might be had by looking through a quill or a piece of 

 rough glass. 



When I was a boy (in 1770), I had an opportunity of amus and te fact. 



♦ I have always found the nostrils below the surface, and the 

 eyes above it ; and I believe there is no great difference in dif- 

 ferent persons. N. 



ing 



