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THE NATIONAL GEOGRAPHIC MAGAZINE 



than are available at present. The unit 

 costs in the report of 1906 are identical 

 with those in the report of 1901, and 

 since 1906 there has been an increase in 

 the wage scale and in the cost of ma- 

 terial. On the Isthmus wages exceed 

 those in the United States from 40 to 80 

 per cent for the same class of labor. The 

 original estimates were based on a ten- 

 hour day, but Congress imposed the 

 eight-hour day. Subsequent surveys 

 and the various changes already noted 

 have increased the quantity of work by 

 50 per cent, whereas the unit costs have 

 increased only 20 per cent — not such a 

 bad showing. In addition, municipal 

 improvements in Panama and Colon, ad- 

 vances to the Panama Railroad, and 

 moneys received and deposited to the 

 credit of miscellaneous receipts aggre- 

 gate $15,000,000, which amount will 

 eventually and has in part already been 

 returned to the Treasury. Finally, no 

 such system of housing and caring for 

 employees was ever contemplated as has 

 been introduced and installed, materially 

 increasing the overhead charges and ad- 

 ministration. 



DREDGING DEVICES IMPRACTICABLE 



Much stress has been laid upon the 

 fact that recent improvements in ma- 

 chinery have so modified conditions that 

 the excavation can be done more eco- 

 nomically b)^ special devices in conjunc- 

 tion with dredging than is possible with 

 the methods now adopted. The ma- 

 chines referred to are for shattering rock 

 under water, and, though it is claimed 

 that such devices have given satisfactory 

 results in connection with the Manches- 

 ter Ship Canal, it is known that similar 

 appliances have failed in certain local- 

 ities in the United States where they 

 were tried. The variations in the char- 

 acter of the rock on the Isthmus from 

 soft argillaceous sandstone to hard trap 

 are such as to make the use of such de- 

 vices very problematical. Experience 

 generally has shown that more money 

 can be wasted on subaqueous rock exca- 

 vation than in the removal of such ma- 

 terial in the dry. Experiments are now 



being made on the Isthmus with one of 

 these rock-crushing devices, but thus far 

 the results are not promising. 



PROBABLE EEEECT OP EARTHQUAKES 



Much has been written recently con- 

 cerning the probable effect of earth- 

 quakes. The last earthquake of any im- 

 portance occurred in the seventeenth 

 century, and existing ruins in Panama 

 demonstrate clearly that no shock of any 

 violence could have occurred during the 

 eighteenth or nineteenth centuries. 

 Should an earthquake visit the Isthmus 

 the chances are that the effect upon the 

 Gatun dam would be less disastrous than 

 upon the Gamboa dam. The solid con- 

 crete construction of the locks, strength- 

 ened by reinforcements, will be as proof 

 against any earth shocks as any structure 

 which man builds anywhere, and the sea- 

 level canal has as much to fear as the 

 lock canal. 



The vulnerability of the lock canal in 

 time of war is another argument ad- 

 vanced in favor of the sea-level type, but 

 has little weight, as the sea-level type is 

 equally vulnerable from attacks by land 

 or air in its Gamboa dam as are tidal 

 locks and the various devices for con- 

 trolling the streams along the route. 



THE OPEN DITCH, PROM SEA TO SEA, AN 

 IMPOSSIBILITY 



The idea of the sea-level canal appeals 

 to the popular mind, which pictures an 

 open ditch offering free and unob- 

 structed navigation from sea to sea, but 

 no such substitute is offered for the pres- 

 ent lock canal. As between the sea-level 

 and the lock canal, the latter can be con- 

 structed in less time, at less cost, will 

 give easier and safer navigation, and in 

 addition secure such a control of the 

 Chagres River as to make a friend and 

 aid of what remains an enemy and men- 

 ace in the sea-level type. 



In this connection attention is invited 

 to the statement made by Mr Taft, when 

 Secretary of War, in his letter trans- 

 mitting the reports of the Board of Con- 

 sulting Engineers : 



"We may well concede that if we could 



