154 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



of each other in the line of sight, another advantage is gained, as any 

 one must admit who notices how much larger, because apparently fur- 

 ther off, the sun is when on the horizon, where there are objects of com- 

 parison, than in the zenith, when there are none. Moreover, as a rule, 

 seafaring men have trained their eyes to estimate distance from a 

 vessel. " 



To the above may be added the views of C. P. Patterson, Superin- 

 tendent of the CJ. S. Coast Survey, given under date of August 31, 1S77, 

 as follows : 



" From my experience, I conclude, and have always safely acted upon 

 that conclusion, that persons on board a vessel, with rare exceptions, 

 judge the vessel to be nearer the land than she actually is, and this 

 arises in a measure from the fact that the eye rarely recognizes the 

 foreground, as it were, of the distances, but is apt, unconsciously, to be- 

 gin estimating the distance from an imaginary line at some distance 

 from the vessel, the higher the eye above the water the greater being 

 this distance, and the greater the real distance of the vessel from the 

 shore than that estimated. This is particularly seen in handling a ves- 

 sel in a harbor, or running close in along a shore. 



"If the eye is placed at the mast-head of a vessel, the horizon rises, 

 as it were, with the eye, the sensation created being that the vessel is at 

 the bottom of a bowl and the eye on a level with the rim, and from this 

 position estimated distances to objects are almost invariably too short. 

 My own custom was to increase estimated distances accordingly. If a 

 man at the mast-head estimated the distance to an object, unseen from 

 the deck, to be 20 miles, I concluded at once that it was 24 or 25 miles. 



" From the shore the eye recognizes a marked foreground (there always 

 being a very decided one, even on a sand-beach of the edge of the break- 

 ers or water), which it cannot ignore, and from which it at once begins 

 to estimate distances. The eye being filled with this l foreground' 

 takes cognizance but indifferently of the object itself, as well as the 

 distance intervening between the outer edge of the foreground and the 

 object, as shown thus : 



A being the elevation of eye above the water, D the edge of the breakers 

 aud foreground, B limit of foreground, aud the position of object. The 

 angle which the eye instinctively measures is D A B, and this is equal to 

 D A 0, be the object wherever it may on the horizon. Then the distance 

 B C is measured only by the greater or less distinctness of the object, 

 there being nothing with which to compare it. From the want of a 

 foreground, if A was the mast-head of a vessel the distance the eye 

 would endeavor to measure is B 0, almost entirely ignoring A D B, and 



