300 



150 feet above the river bed. Five sluicing outlets, each con- 

 trolled by a 5x5 foot sliding gate, are also provided at river 

 level. All these outlets are operated from control chambers 

 inside the dam. 



A system of inspection galleries of which the control chambers 

 are a part give access to the dam at several elevations, the lowest 

 of wdiich is 230 feet below normal high water surface in the res- 

 ervoir. The capacity of the reservoir is 244,300 acre-feet, or 

 about 79,600,000,000 gallons. This reservoir is 18 miles long 

 and extends up two forks of the river. When needed for irri- 

 gation the water is carried down 12 miles in the channel of the 

 river to a low diversion dam and from there taken out over the 

 land through a network of canals and laterals. In this way 

 234,000 acres of sagebrush desert is to be converted into gardens, 

 orchards and farms. 



The principal quantities involved in the construction of Arrow- 

 rock dam and the spillway are as folows: Excavation, 683,000 

 cubic vards ; concrete, 610,600 cubic yards; reinforcing steel, 1,- 

 350.000 pounds; gates and structural steel, 1800 tons. 



All this work was executed under the general direction of F. 

 E. Weymouth, supervising engineer of the U. S. Reclamation 

 Service, with Charles H. Paul, construction engineer in direct 

 charge, and James Mtmn, superintendent of construction. 



A BACTERIAL MANGO DISEASE. 



In the Annals of A])plied Biology II, \)\). 1-14. .says "W. N." 

 in the Agricultural News, appears an account of a detailed re- 

 search on a disease of mangoes in South Africa by Ethel M. 

 Doidge, I\I. A., F. L. S., Mycologist, Division of Botany, Pre- 

 toria. 



The virulence of the disease is such as to thrcilcn seriously 

 to affect the export trade in mangoes. A large i)ercentage of the 

 fruit falls to the ground whilst yet immature, and the mangoes 

 which remain on the trees ar rendered imsightly and imfit for the 

 market. The disease was first reported from Barberton in the 

 Transvaal in 1909 and is said to have appeared there after a hail- 

 storm in 1906, the infection .starting in a corner of an orchard 

 and spreading rapidly with the prevailing winds. In 1908 not a 

 single fruit was obtained from sixty trees. Each season since 

 the disease has been steadily gaining groiuid. No record lias 

 been found l)y the author of rmy similar afTecti'>n in oIIkt parts 

 of the worlfl. 



The flamage done is mainly to the fruit. Infection also occurs 

 on leaves and branches. ])roducing lesions in which the bacterium 

 is carried over from one crop to the next. Hn the leaves small 

 angular w.'itcr-soaked areas, some 2-3 mm. in diameter, appear, 

 whicli later become dark brown ; the surface is somewhat raised 

 and shining and fre(|uently there is a slight exudation of gum. 



