62 HARBOUR CONSTRUCTION. 



Commander W. U. Moore, R.N., thus describes the bore of the 

 Tsien-tang-Kiang : 



" While the flood tide is travelling across the sands, the water is 

 rising steadily at the end of the navigable portion of the Hang-chau 

 gulf ; and by the time the two branches of the bore join there is a 

 difference of level of 19 feet, at springs, between the water on the 

 outside of the bar and that in the mouth of the river, a distance, in a 

 direct line, of about 20 miles. Accordingly, the flood enters the river 

 down a gradient of 1 foot in a mile with great force, and is assisted 

 by the transmitted pressure of the advancing tidal wave in the 

 estuary. The speed, as measured by the officers of H.M.S. Rambler, 

 is 12*7 knots, or 14'6 statute miles, an hour. The bore has a breadth 

 of 9 cables, or 1800 yards, and its front is a gleaming white cascade 

 of bubbling foam, 8 to 12 feet high, pounding on itself and the river 

 in front of it at an angle of from 40 to 70, the steepest and highest 

 portion being over the deepest part of the river, where the outgoing 

 stream has the greatest velocity. 



" The noise is not the least impressive feature of the phenomenon. 

 On a calm, still night it can be distinctly heard, when 14 or 15 miles 

 distant, an hour and twenty minutes before arriving. The noise 

 increases very gradually, until it passes the observer on the bank of 

 the river with a roar but little inferior to that of the rapids below 

 Niagara. 



" The bore maintains its breadth, height, speed, and regular 

 appearance for 12 or 15 miles above the mouth of the Tsien-tang- 

 Kiang." 1 



1 Min. Proc. Inst. C.E., vol. xcix. 



