50 THE TIDES OF THE BAY OF FUNDY—MURPRHY. 
bore. Further down the river widens and receives easily the 
tidal wave from Cumberland Basin. As it ascends the stream 
it becomes more confined and crowded, until, from its own 
gravity, it rushes swiftly forward—hence the phenomenon we 
have witnessed. 
Out in the Bays of Chiegnecto and Cobequid these flood 
tides exhibit different forms and phases, varying with the vari- 
able contour of the shore. At low tide spurs indicating shallow 
channels, estuaries and creeks, are conspicuous, with miles in 
extent of dry flats and marshes, looking as if the sea had 
altogether retired. Presently, however, the returning flood tide 
appears in the distance, tumbling and rolling with white breakers 
abreast. It rushes swiftly forward and digs deep into the red, 
soft mud, that but momentarily obstructs its advance. It fre- 
quently resembles the rapids of a great river, stretching across 
for miles, with alternating patches less turbulent, where in its 
path it meets with less resistance. Thus this tremulous tidal 
oscillation, with breakers tumbling from and over its crest 
threatening to overwhelm and engulf everything that impedes 
its progress, moves bodily onward until it reaches the heads of 
Shepody, Cumberland and Cobequid Bays. The mud flats are 
soon covered, and the creeks, estuaries and basins are full to the 
brim,—the fiat has been given, “ Hitherto shalt thou come, but 
no further.” Immediately the retreat commences, and the 
waters retire almost as rapidly as they came. 
The flood tide carries with it the silt and mud, and deposits 
its load chiefly in the creeks and on the flats at the head of the 
bays. AsI hada good opportunity of ascertaining the extent 
of this deposit, and although it is a digression from the subject 
of this Paper, it may be worth placing on record here. The 
old wooden bridge that crossed the Avon River at Windsor is 
being replaced by an iron bridge. The substructure consists of ° 
five pairs of steel cylinders, each tube having an internal 
diameter of five feet, and are secured to the limestone rock on 
which they rest. The bottom sections of these tubes stood, when 
placed in position, from three to six feet above the level of low 
tides, and were filled with concrete to a height of two feet, 
