Topographic, Triaonometric and ieodetic Sur ve, in. Irrigation Engineering - PREFACE TO SEVENTH EDITION - THE first edition of Irrigation Engineering, was a pioneer in its field, and quickly took its place as the recognized standard therein, as indicated by its passage through six successive editions. At the date of the first edition and in fact, some time later, the large irrigation works of engineering interest were mostly in India and Egypt. Mr. Wilsons familiarity with those works, based largely on personal contact with them and their builders and operators, gave the early editions of his work a special value as contributions to western knowledge of this subject. The subsequent activity in irrigation in other parts of the world, especially in the United States, together with similar developments in related lines of municipal water supply and hydro-electric construction, have presented new problems and evolved new solutions of old ones to such an extent that what might almost be called a new science has been developed, requiring different treatment. Moreover, social, political and economic conditions in America are radically different from those in the Orient, and this imposes very different conditions and limitations upon the practice of irrigation engineering. Sir William Willcocks, on his visit to America, said he was accustomed to look upon the irrigation industry as one absolutely dependent upon cheap labor like that of Asia and Africa, and that his chief interest in examining American irrigation was to learn how it - was that irrigation could be practiced at all in America. American irrigation practice therefore is very different from that of India, and has been largely developed quite recently. V Yhcn tlicl untlci-hignctl . as rcclucitecl to re-isc, this vorli for a scvcnth etlition. 11e untlvrtooli the rasl untler the l antlicap oi having iis time -er-lully occu ie 1 d y otiici ll duties. witllout full. realizi ig tllc magnitude of the task. 7 he natcrial of the sistli cciition relating to sewage disljosnl ancl irrigation and t o sul tcrranean water su1 1 1-has 11ec. n liberall. usecl. . A fen other portioils ha-e hccn uset1 in part. ant1 about 40 per cent of the illustrations have been utilizctl. In the main the vorl has I c e ire w ritten ant1 rearranged, ant1 much new material has 1 een adtletl. Ihe principal diiierence introducecl is the treatment oi soils. plant food, operation irncl maintciiance, and other lirles of work where the tluties of the irrigatio l enginecr comct in contact ivith tlii irl-igator, such as the pre1 u ltion of I ncl. the duty of water ancl its application to the lantl. S o attempt hiis been made to treat these nor intleecl any other 1, ranches of the sul ject exhaustively, which cannot 11c clone withi11 the limits of sucli a worl as this. I t is lioljcd the results justifthcil- uIjlic tiona, n d will continue the usefulness of the v. orl so well pio icered by 1Ir. IYilson. Tn writing and com1 iling this work niuch assistance has of coursc ljeen tlra vn from existing literature, ant1 rcicbrc lcc.. arc made to the same a t the ends of clia ter a s n , d in tlir. test. A. 1. 0. TABLE OF CONTENTS I. Ii, rc. c. nt ic in Soils. . . . . . . . . . . . . . . . . h. liesi-l an i. I I T . ariou- rol15.. . . . . . . . . . . . . . . . . . . 6. 1Zrrneilic. s ior . ll ali . . . . . . . . . . . . . 1. l, c clii1 . 1. . . . . . . . . . . . . . . . h. Iloivin. . . . . . . . . . . . r. ro-tl , i i S i i t i i 1l 1t 11 it . . . . . . . . . . . . . if. I I C I I I I . . . . . . . ,, c l. Ul11. . . . . . . . . . . . . . . . . . . . . . . . . . . . SOIL II IsTI. RI . .. . . . . . . . . . ...