1907.] THOMSON— PROGRESS OF THE ISTHMIAN CANAL. 127 



favored by many of the foreign engineers, while the decision of 

 Congress to build a lock canal was made, as is well known, in 

 accordance with the recommendation of the American engineers. 

 The ^yriter does not profess to be able to judge between these two 

 schemes. It would be presumption for one who, though much of 

 his work has been engineering of a special kind, is not experienced 

 in civil engineering, much less in such matters as have divided the 

 opinions of many of the foremost engineers of the time, who have 

 been called upon to devote a long period to their consideration. All 

 that is attempted to be recorded here is an impression; which may 

 not be worth much. Still it is an impression. The writer had 

 previously in common with many others, conceived the idea that it 

 wouki be a mistake to build any other than a sea-level canal, but 

 upon arriving at the site of the Gatun dam, and witnessing the 

 conditions, this idea soon gave place to a feeling that the lock 

 canal project was probably a correct solution. Nothing has since 

 been learned tending to change this impression, which, in fact, 

 was more and more confirmed or strengthened as the further in- 

 spection of the work in the zone was pursued. 



The problem of the Chagres River floods which was so serious 

 in the case of a sea-level canal solves itself in the lock canal, with 

 the dam at Gatun. This structure when completed will impound 

 the river water even in heavy floods and form above the dam a 

 great fresh-water lake of about one hundred and ten square miles 

 in area, the level of which will be about 85 feet above the sea. For 

 about twenty miles ships will be able to steam at good speed in 

 this elevated lake and make up for time lost in passing the locks, 

 so that the actual time of passage through the canal may not differ 

 greatly from that which would have been needed in the case of a 

 sea-level construction. On the right of the proposed dam, as one 

 faces Colon, was seen the site of the three great locks, which will 

 be built in flight and in duplicate. In fact, the work of excavating 

 for them had been begun, as before stated. The locks being in 

 duplicate will permit simultaneous passage of ships both ways, or 

 up and down. They will be of size enough to accommodate, with 

 considerable margin, the largest vessels in existence ; greatest length, 

 breadth of beam and draught. 



