IRREGULAR SURFACES. 195 



960 feet to an inch, and represents a plot of 80 acres, 

 being 2,640 feet, (half a mile), in length, having 22 fur- 

 rows, 120 feet apart, in that direction ; and 1,320 feet, 

 (quarter of a mile), in width, and having 8 check fur- 

 rows, 165 feet apart, in this direction. 



For those cases in which an irregular surface cannot he 

 avoided the arrangement of the water furrows is different. 

 For a field which slopes on either side from a central 

 ridge the arrangement is made as follows : (See fig. 82.) 



The water is brought from the main primary ditch, 

 on to the highest portion of the ridge. From this it is 

 carried by a principal furrow along the ridge, and then 

 by other furrows, a, a, on each side down the slope, and 

 from those into distributing furrows, c, c, nearly parallel 

 with the main furrow, and in the manner before describ- 

 ed for the bedding system applied to gardens. Thus the 

 water flows down the slope on each side in a series of 

 channels provided for it, according to the circumstances 

 or necessities of each case. 



Where the surface is irregular in every direction, it is 

 necessary to discover by careful leveling the course to be 

 taken by each main distributing canal, which should be 

 made the boundary line between the fields on either hand, 

 and will therefore be a permanent construction. The 

 course of the canal will be such as to give it the least 

 possible slope, so that none of the head of water may be 

 lost in distributing it from the end of the canal. It is 

 obvious that this course should be laid out with great 

 care and exactness, lest by losing some of the head, some 

 portion of the land should be left without water. This 

 work should be done either by a competent surveyor, or 

 by the assistance of instruments in the hands of the 

 farmer competent to use them. There is no particular 

 skill required to do this ; it is rather a work that calls for 

 extreme care and patient verification. The instrument 

 used may be a surveyor's field or portable level, which will 



