224 



TORONTO HARBOUR— ITS FORMATION AND PRESERVATION. 



[1854. 



the Don, and that the delta lias thus been raised above the sur- 

 face of the water and extended westward far beyond its original 

 limits. 



The effects produced by waves on a shore exposed to their 

 action are of various kinds, depending in a great measure on the 

 nature of the beach, the direction of the waves, and their me- 

 chanical force: if the shore be of clay the action is entirely 

 destructive, the banks are undermined and continually caving in, 

 the fine argillaceous particles are taken up by the water, carried 

 out and deposited after a time at depths unaffected by the mo- 

 tion at the surface ; if the shore be of sand or gravel the effects 

 produced are quite different. When the direction of the waves 

 is not at right angles to the beach a progressive action results, 

 and when the waves break point blank on the shore line with 

 sufficient force the action is destructive, in which case the banks 

 are broken down and the spent wave returns loaded with sand 

 to be deposited outside of the breakers in the form of a shoal 

 generally parallel to the coast ; if the soil of which the banks 

 are composed be a mixture of clay and sand the action is both 

 destructive and progressive, the clayey particles are washed out 

 and deposited in still water, while the sand, gravel, and stones 

 are left behind to be moved forward either in one direction or 

 another, and at a rate depending solely on the strength of the 

 impinging waves, and the gravity of the materials themselves. 

 On a rocky shore the effects produced are precisely similar, 

 although of course to a much more limited extent ; by continual 

 exposure to the wearing action of water and weather a mass is 

 undermined and tumbles clown, a portion of the debris is put in 

 progressive motion during every storm when the waves impinge 

 otherwise than at right angles to the shore line, and is moved, 

 according to the locality, in a certain prevailing direction, until 

 meeting a projecting point or other hindrance to its onward 

 progress; thus forming those shingle beaches seen at many 

 places on all rocky shores. 



The effects of the destructive action on banks of clay can be 

 traced wherever the shore is entirely of that material ; the owners 

 of property along many parts of Lake Ontario can bear testimony 

 to its annual encroachments ; and, to come nearer home, many 

 citizens of Toronto must have witnessed the gradual alteration 

 in the form and recession of the clay banks between the old and 

 new garrisons. 



The effects of the progressive action can also be witnessed at 

 many points on all the lakes; but at none in a more remarkable 

 degree than at Toronto, although at other places to even a much 

 greater extent. And since to the peculiar motion of sand and 

 gravel beaches will be attributed not only the extraordinary 

 changes the Peninsula is at present undergoing, but even the 

 greater part of the entire formation, it will be necessary to ex- 

 plain fully the nature of it, and give the reasons why the beach 

 should have a tendency to move in one direction in preference 

 to another. 



Let us take an example when the direction of the wind forms 

 an acute angle with the shore, a particle of sand resting on the 

 surface is driven forward up the inclined plane of the beach in 

 the direction in which the wave itself moves, the particle either 

 remains at its now elevated position or (as is more usual) sweeps 

 along in a small curve and rolls downwards with the expended 

 wave to a new position, the distance of which from the first will 

 be in proportion to the mechanical force of the wave and its 

 direction; another and each successive wave drives the particle 

 forward in a similar manner, unless by accident it finds a resting 

 place behind some obstruction or be buried by other particles on 

 the same mission as itself. If we take instead of a grain of sand, 



a small pebble, we find that the same wave, or a wave having the 

 same force, moves it a less distance than it does the sand, that 

 larger pebbles being heavier make proportionately less progress, 

 and that stones still heavier are moved only when the waves 

 have considerable power. All of these bodies, however, when 

 within the impelling force of the wave and placed in positions 

 fairly exposed to its direct action, seem to be governed by the 

 same law, and are moved forward a less or greater distance ac- 

 cording to their weight and gravity. 



X 





Tlie arrows denote the direction of the waves ; the dotted lines show 

 ike paths of grains of sand and pebbles. 



The zig-zag direction taken by the sand and gravel on the 

 beach is indicated by the various dotted lines on Fig 2, the 

 smallest one is intended to show the course of a grain of sand, 

 and the two largest lines that of pebbles varying in size. The 

 progressive motion is slightly suspended between each wave, but 

 although intermittent is continued so long as the sea breaks on 

 the shore from the same quarter, and until the moving mass meets 

 with an obstruction, or by reason of a sudden bend or other 

 peculiarity of the shore line is deposited in a position beyond Ihe 

 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 laterally 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. 



\ 



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

 onward 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, un- 



