292 Ml-. 10. W. Gudger on (he 



tliis fish takon hy itself in tlie place it requires. l?ecause 

 tlie rudder is small and placed at one end of the boat it is 

 managed by one man who does not exert himself greatly. 

 In the same way it is easy for that uhich moves one end to 

 move the whole, for as the force and swiftness of those 

 things which are thrown or moved finally ceases, so at the 

 end of a continuous thing in motion the movement is weak 

 and feel)le, and because it is weak it is easily disturbed and 

 overcome. As a boat, which is a continuous thing, goes 

 very swiftly when driven by the winds, the first end called 

 tiie prow goes more rapidly, and the rear end called the 

 stern goes not so raj)idly for in this latter place is the rudder 

 which, moved here and there, makes the prow move easily 

 also, for the reason above mentioned, and consequently the 

 vessel as a whole moves. In this way, if a vessel is lightly 

 driven straight ahead, and if the Eeheneis or Hemora, 

 having put its mouth against the rudder, moves it here and 

 there, it is necessary that this movement through the con- 

 tinuity of t!ie vessel be communicated also to the prow and 

 that it stop in its first course to waver in this direction or 

 that according as the fish moves it ; for it is a thing proved 

 by reason, and certified by experience, that however little 

 one of the ends is moved, the other also and indeed the 

 whole of any continuous body is moved in the same way." 



In this Kondelet seems to have taken from Aristotle's 

 treatise on Mechanics the hitter's explanation of how a rudder 

 causes a ship to change hei' course, and to have adapted it 

 as seen above to try to show how the Eeheneis causes a ship 

 to change her course and be delayed. 



The above is a good translation of Rondelet's old and very 

 difficult French *. In another place, speaking of Oppian's 

 Hemora, which he identifies as the lamprey eel, and which is 

 said to stop and hold b;ick vessels, Rondelet affirms that 

 this is "a thing which corresponds to our lamprey and 

 which I have known through experience, for if it puts its 

 mouth against a boat it stops it, and I have seen it thus/' 

 Here for the first time we have an eye-witness account of 

 the ship-retarding |)0\\er of a fish. 'I'he lamprey has a round 

 suctorial moutli by which it transports stones to make its 

 "nest" at the breeding-season, and by which it fastens 

 itself to fishes. That it should tiius fasten on to a vessel is 

 by no means improbable, nor is it improbable that by violent 

 motions it could slow up the speed of a small boat. 



The ' De Subtilitate Rerum, Liber X.' of J( ronie Cardan 



* For this translation I am indebted to Miss Ilinda Hill, head of the 

 Department of French in this College. 



