M//(h of the Ship-holder. 297 



3 feet to the sliaik's G. Argument is not needtd to establish 

 the idea of a " brake." Tlie figui'e is from a note by K.. I. 

 Geare in ' Seientific American' for 190!i. Mr. Geare 

 remarks that the shark often becomes " emaciated from tlie 

 strain of pulling these uninvited guests around.'^ However, 

 it should be stated that in the figure here given thcEeheneis 

 is much hirger in proportion to the size of the shark, so far 

 as my experience goes, thau is the case ordinarily. Echeneis 

 is known to attain a length of 3 feet. A Rcmora half that 

 size would be extraordinarily large. On the other hand, 

 however, mention should be made of the fact that, while 

 these semi-parasites are small, not infrequently several may 

 be found on one shark. On a shark taken at Tortugas I 

 found three, while one at Key West was infested with four, 

 the largest about 30 inches long. 



Scattered throughout ancient and mediaeval literature are 

 a number of more or less isolated explanations of submarine 

 clitfs, of magnetic rocks, and of supernatural ai.-d inexplicable 

 forces which held vessels as if anchored. These are widely 

 scattered and little emphasized, and it does not seem worth 

 while to go into them. A fair example is that of Kecker- 

 uianu (1614), who alleges that the Rcmora sticking to the 

 stern of the \essel pours out a very viscid and cold humour 

 which cavises the water around the rudder to be congealed, 

 making the vessel to lose steerage. Again, Johnston (1057) 

 notes that the lod( stone has the power of attracting things, 

 and thinks that the Remora has some such non-understand- 

 able power. 



Fourth Explanation: '"' Dead- Water. ^' 



From the foregoing accounts no one can doubt that a 

 school of Remoras attaching themselves to a small vessel 

 can seriou>ly arrest it in its course, but that they could 

 noticeably retard a large sailing-vessel or a steamer is absurd. 

 However, there is not lacking evidence from the days of Pliny 

 to the present time that large sailing-craft and in our times 

 even steamboats have been mysteriously checked in their 

 courses and even stopped almost or quite still. These being 

 facts, it is necessary to find an explanation for them. This 

 is to be found in the " Dead-Water" of sailors. 



The phenomenon of '' Dead-Water," in which a sailing- 

 vessel loses velocity and in a light wind may even come to a 

 stop, and in which even a steamer may be retarded, has long 

 been known to seamen. Probably the earliest notice of this is 

 to be found in Chapter X. of the * Agricola' of Tacitus, where. 



