SOUNDINGS AND HYDRAULIC SURVEYS 17 



the cubic content of each compartment is accurately measured and 

 the solidity of the various compartments of the scow taken as the 

 base for estimating the amount of the dredged material. When 

 instead of scows, the dredge is provided with hoppers, the cubic 

 content of the various hoppers are used for the measurement of 

 the material excavated from the bottom. 



The amount of the excavated materials deposited into the scows 

 to be transported to the dumping place can be also measured 

 from the draft of the scow itself. There is no doubt that the 

 more material deposited into the scow the greater will be its 

 draft; 'by gauging the draft of the scow when empty and when 

 it contains a certain determined load of 100 tons, for instance, 

 the difference of the two drafts will indicate the content of the 

 load and from these two points a scale can be made for the frac- 

 tions of the load as well as its multiples. From this graduated 

 gauge the content of the scow can be easily deduced. 



In the construction of the new stone breakwater at Buffalo, 

 N. Y., all the stones were paid for by the ton, and were transported 

 by means of scows, either of the deck or dumping type. For the 

 purpose of measuring the amount of material transported, each 

 vessel was provided with glass gauges and graduated rules by which 

 the draft of the vessel was ascertained. A number of deck scows were 

 built especially for the work and exact measurements of these vessels 

 were made before launching. From the data thus secured elaborate 

 tables were prepared showing the displacement for every y^ of 

 a foot, calling the bottom zero. 



The glass gauges were placed on the keel forward and aft, and 

 consisted mainly of a wrought-iron standpipe 3 in. in diameter, 

 into which two brass cocks are screwed. Between the cocks, which 

 are from 4J to 7 ft. apart, depending on the sizes of the scows, was 

 placed a glass tube about 1 in. in diameter, the whole apparatus 

 resembling a water glass gauge as used on a boiler. A wooden rule 

 graduated in feet, tenths and hundredths was attached alongside 

 of the glass tube. 



The graduations of the rule corresponded exactly with the draft 

 of the vessel. This was usually accomplished by taking the mean 

 draft of the vessel fore and aft, and setting the rules to correspond 

 with the water in the gauge. Absolutely quiet water was required 

 for this work, and to facilitate it marks 6 in. apart were accurately 

 cut into the sides of the vessels at each end. To determine the load 



