Mr. Gisborne, in his report, devotes some space to speculations on these results. “There can be no doubt,” he remarks, “that at high water there will be a current from the Pacific to the Atlantic, and that during the ebb tide there will be a current in the opposite direction. The extent of these currents, and the place of their greatest effect, depends on the comparative sectional area of different portions; and if the cross-section is uniform throughout, will be some time after high tide in the Pacific and at the Atlantic end of the canal. The phase of the tide wave (or the appreciable effect of the tide) will take one and one-half hours to reach from one end to the other, and presuming the current to be uniform in the whole length”——“the question may be examined as a maximum, _i. e._, what will be the surface velocity of a canal thirty miles long, having a fall of eleven feet, or with a horizontal bottom having at one end twenty-eight feet, and at the other thirty-nine?” Employing Du Buat’s formula, with the following quantities: Mean depth 35.50 feet. Mean width 183.50 “ Mean border 244.80 “ Area water section 6,147.255 “ Hydraulic mean depth 25.11 “ Fall per mile 0.33 “ he deduces a maximum surface velocity of three miles per hour. The assumed average fall per mile is strictly a variable function, and at its maximum would give a result greatly in excess of that deduced by Mr. Gisborne. There is no reason for this assumption of a fall of 0.33 of a foot per mile. It directly involves the question to be determined, since the velocity depends upon the inclination of the surface. The value deduced by the formula is not the maximum but the minimum velocity attained in the canal upon the assumed fall per mile. There is another error in Mr. Gisborne’s statement. “The tide,” he remarks, “would take one and one-half hours to reach from one end to the other, presuming the current to be uniform; what,” he asks, “will be the surface velocity in a canal thirty miles long?” This statement contradicts his calculations, and involves also the question at issue. If the tide travels to the end of a canal thirty miles long in “one and one-half hours,” it is evident that it must move at the rate of twenty miles per hour, a velocity which renders Mr. Gisborne’s strait impracticable for navigation. In fact, neither assumption is tenable. The problem is very complex, or, rather, with the data given, indeterminate. It is well known that the tide is propagated up the channel of a river in a succession of long waves, or swells, and that when the tidal wave is entering the mouth of the river, the waves which have reached the head are returning. The same movement is observed, on an exaggerated scale, in the successive breakers which roll in to meet the one which is returning, after it has expended its force upon the beach.