_The proposed Panama Canal locks._—The original plans of the Panama Canal provided for a waterway that should be 28 feet below the mean ocean level throughout its entire length. It has since been found that this design would involve an enormous expenditure and a serious delay, and hence the decision in 1888 to provide a series of four locks on the Pacific, and four locks on the Atlantic side. On the Atlantic side, two of the locks were to have a fall of 8 metres (26 feet 5 inches), and two others a fall of 11 metres each (36 feet 3 inches), while on the Pacific side, three locks were to have a fall of 11 metres each (36 feet 3 inches), and one a fall of 8 metres (26 feet 5 inches). The height of the water level on the Pacific side would, therefore, be 41 metres (135·6 feet), and on the Atlantic side it would be 38 metres (125·7 feet). The width of the lock gates was to be 18 metres (59·5 feet), and the length was 180 metres (595·5 feet). The locks and their gates were to be constructed in iron, and it was estimated that 20,000 tons of cast, and 15,000 tons of wrought, iron would be employed in their construction. The effect of this modification of the original plans would, of course, be to reduce the amount of excavation necessary in the Culebra cut by at least one-third, but it would also obviously alter the entire character of the canal as first projected. The opinion of some engineers appears to be that the frequent opening and shutting of the sluice-gates, with such a considerable pressure of water, would not be without a certain amount of danger. The pressure would be increased little by little until it had been raised to a breadth of 10 metres, and even as much as 15·40 metres. It is not unusual to find a pressure of this extent at dock gates, but in the largest canals hitherto constructed with locks, the pressure has seldom exceeded three to four metres. In order to meet similar cases, it has been proposed, where there was a constant use of a canal at all hours of the day and night, to employ a very large number of small sluices adapted to the slopes of the canal. This expedient has been put in practice in the case of the eight successive sluices known as Neptune’s Staircase, on the Caledonian Canal, and, on the Canal du Midi in France, in the case of the seven sluices of the staircase of Béziers. It is, however, held by _Le Génie Civil_ that such small sluices, although more easy to open and offering perhaps greater resistance, are, nevertheless, not well adapted to the necessarily rapid and constant working of a canal like that of Panama. This expedient having, therefore, been abandoned, there remained that of movable caissons suspended by the upper part, which is known as the Eiffel system. This system, with its movable gate shut, and the recess into which it fits when open on the right, is illustrated in one of the drawings attached to this chapter, while another drawing shows the lock gate open.