8 BULLETIN 194^ U. S. DEPARTMENT OP AGRICULTURE. 



were those used by the writer and his assistant, Mr. Ernest C. For- 

 tier. Where those used by his associates were essentially different, 

 the fact is mentioned. 



EQUIPMEnSTT. 



Tapes. — Linear measurements for length of canal tested were made 

 with a high-grade steel tape, 100 feet long, graduated to tenths of a 

 foot. This tape was also used to determine widths for current-meter 

 measurements for canals more than 25 feet wide and cross-section 

 data for canals more than 50 feet wide. For canals under 25 feet in 

 width the measurements of widths in determining the discharge were 

 made with a small steel tape, 25 feet long, graduated to hundredths 

 of a foot. For taking cross sections on canals less than 50 feet in 

 width a 50-foot cloth tape containing strands of wire was used. 



Level. — The writer used a new 18-inch Berger engineer's wye level, 

 equipped with a bubble whose sensibility was rated at 10 seconds of 

 arc for 1 division of scale equal to one-tenth of an inch. The bubble 

 vial was 6.5 inches long. The telescope power was 35 diameters. 



Rod. — A new Philadelphia rod, equipped with rod level and with 

 vernier reading to thousandths of a foot was used in the determina- 

 tion of the fall between the bench marks at the upper and lower ends 

 of the reach tested. 



Current meters. — Two new small Price cup current meters were 

 used. They were identical in construction, of the combination type; 

 that is, each meter was so equipped that a single or a penta head could 

 be used. The single head records each revolution of the meter and 

 is adapted to water flowing up to about 5 feet per second. The penta 

 head records each fifth revolution of the turbine and is used in high 

 velocities. Both of these meters were rated on both rod and cable 

 by the United States Bureau of Standards at Chevy Chase Lake, Md. 

 They were carefully rated, as it was understood that they would be 

 used for research work. One of these meters was used constantly, 

 throughout the summer, the other one being very carefully cared for 

 and rated against the one in constant use at intervals throughout the 

 summer, so that any variation of the rating curve could be detected 

 early. At the end of the season the one in use was again rated by the 

 writer, at Calexico, Cal., and it was found that if any change had 

 taken place it was too small to necessitate a change in the table. 



The meters could be used on either rod or cable. Eight 1-foot sec- 

 tions of rod, graduated to tenths of a foot, were carried. 



When the meter was used on a cable the lower 18 inches of cable 

 was replaced with a section of strong piano wire, with a swivel har- 

 ness-snap connection to the hanger rod attached to the meter. 



Two 6-pound lead torpedo weights were carried, while it was found 

 necessary to use 24 pounds of lead in the New York Canal, with veloci- 

 ties up to 6.6 feet per secoijd in depths of 6.62 feet. 



