REPORTS ON TORONTO HARBOUR. 



19 



sudden bend or other peculiarity of the shore line is deposited in a 

 position beyond the influence of the waves. 



When the waves impinge at right angles to the shore the progressive 

 motion of the beach is theoretically nothing, the various particles of 

 sand are rolled upwards and downwards, changing position only later- 

 ally or in the line of direction of the waves ; when the waves impinge 

 somewhat less than a right angle the grains of sand move along in a 

 sharp zig-zag line, as 



Fig. 3. 



W" 



in Fig. 3, when much less than a right angle the particles move on- 

 ward in a long undulatory line as in Fig. 4. The distance between 

 the points of each indentation being in proportion to the cosine of the 

 angle formed by the direction of the waves and the line of the shore. 



Fig. 4. 



Granting that the direction of the waves is governed by that of the 

 wind, it follows that whenever the wind blows from a quarter to the 

 right of a perpendicular to the shore, the beach sand is moved to the 

 left, and vice versa. If, therefore, the wind blew with equal strength 

 and during equal times from all points of the compass throughout the 

 year, and the waves also had at all times the same mechanical force, 

 the sand would at one time move to the right, and at another time an 

 equal distance to the left ; but, to speak in general terms, the beach 

 would remain ever as it was (excepting the effects of the destructive 

 action). Since the forces never could act simultaneously, we would 

 have, it is true, a constant repetition of complicated motions, zig-zag, 

 undulatory, lateral, progressive, and retrograde; but, from their as- 

 sumed equality and the equal times of their application, there could be 

 no resultant. The mean velocity of the wind may properly enough be 

 taken as equal throughout the year from all points of the 7 compass, 

 since the actual difference, as obtained by observations, will effect the 

 results inappreciably; but the mean force of the waves will not in 

 consequence be equal, as this is greatly influenced by the locality. It 

 Is found that the mechanical force of a wave depends chiefly on the 

 strength of the wind and the extent of open water traversed; allowing 

 then that the wind blows equally from all points, it will follow that 

 the resultant of the aggregate forces of the waves impinging at any 

 particular place, will be a line lying in a direction opposite to the 

 largest area of open water. 



In applying this conclusion to the beach in front of Toronto we find 

 that the greatest extent of Lake Ontario passed over by winds blowing 

 from any point westward of the perpendicular A B, Fig. 5, does not 

 exceed forty miles, nor is the area of water over twelve hundred square 

 miles, while to the East of A the 



Fig. 5. 



waves have a fetch of as much as a hundred and eighty miles over an 

 expanse of water measuring nearly nine thousand square miles ; hence 

 then (the duration of the action being taken as equal in both cases) 

 the intensity of the collective forces of waves impinging at A from the 

 eastward is many times greater than those from the westward, and the 

 motion of the beach at A must therefore be westerly; it must of course 

 move with a variable velocity because the forces are not constant; its 

 path, or rather the path of each particle, undulatory, since the forces 

 act impulsively on the plane of the beach in combination with gravita- 

 tion ; it must sometimes retrograde since the direction of the forces is 

 ever changing, and they never act simultaneously ; but aggregately, 

 the beach sand, subject to many complicated motions, and acted on by 

 innumerable and incalculable forces, must move absolutely from east 

 to west, and (taking the forces on each side of line A B respectively 

 as positive and negative) with a velocity proportionate to their alge- 

 braic sum. 



On that portion of the beach successively washed by the waves only, 

 can the progressive motion be proved occularly, yet doubtless a similar 

 action must be produced between the breakers and the main land all 

 along the shore, and when we consider that the lake is seldom or never 

 entirely at rest, that even during perfect calms, unless continued for 

 several days, a gentle ripple capable of moving sand is found on the 

 shore, throughout the whole year, therefore, must the materials com- 

 posing the beach be continually changing place, and although some- 

 times°moving easterly, yet generally, as proved above, in the contrary 



direction. 



Fig. 6. 



The accompanying drawings of natural groynes very strongly con- 

 firm the conclusion here come to. They are copied from sketches 

 recently taken (1850) on the spot, between Privat's Hotel and the 

 Scarboro' Heights. Fig. 6 was formed by the falling of a tree opposite 

 a fisherman's hut east of the Narrows on the passing log: the outer 

 end of the tree was supported by its branches : about one half of the 

 log was floating, but kept stationary by the tree; the remaining half 

 rested on the surface, and enabled the sand to accumulate at its easterly 

 side. Figs. 7 and 8 appear also to have been formed in a similar 

 manner. They were found on that part of the shore between Ash- 

 bridge's Bay and the Scarboro' Heights. The dotted lines indicate what 



Fig. 7. 



