230 [Senate 



easier to attarh two sights at the ends of the cross bar, and take 

 longer observations, a rod, marked at a height equal to the height 

 of these sights, being held at a distance by an assistant. 



Such a level mav be made to close, like a pair of compasses, when 

 when not in actual use. If the points are accurately one rod apart, 

 the operation of measuring the distance is combined with that of 

 leveling. 



Precautions needed. — Irrigation, like every other farm operation 

 of importance, needs to be conducted with care and skill. A want 

 of judgment or proper intelligence, may in some cases lead to failure, 

 or greatly lessen advantages. 



Practice has fully shown that too long a continued and heavy 

 flooding of upland plants, is actually prejudicial to their growth. 

 The plants should enjoy the full benefits of both air and water. 

 There is no better way of accomplishing this object than to keep the 

 water constantly passing over the surface in a tolerably brisk current. 

 It must not be so rapid as to wash away the soil, nor so slow as to 

 stagnate, or to drown the plants. It is only while water is in motion 

 that plants are enabled to draw from it to advantage by successive fresh 

 supplies the nutritive substances it contains in solution. A farmer ac- 

 customed to the appearance of plants when in the most rapid and 

 healthful state of vegetation, will detect at a glance any injury which an 

 overdose of water may occasion, when the supply should be withdrawn. 

 Excessive irrigation may also prove injurious where it produces a wa- 

 ter-soaked subsoil, the remedy for which should be draining. Indeed, 

 so different in nature is a water-soaked and an irrigated soil, that while 

 the former injures, the latterbenefits ; the former state resulting from 

 a want of draining, and the latter always proving most eminently bene- 

 ficial on well drained land, where stagnant water can never accumulate. 

 Equal success has not always attended irrigation, in consequence 

 of the different quantities of enriching matter contained in different 

 streams. The most valuable, usually, are those which have passed 

 through a thickly populated country, and have received and become 

 saturated with different kinds of waste manures. Hence the drainage 

 of sewers, and the washings of roads, are particularly valuable. 

 Sometimes, however, there are fertilizing substances derived from 

 the soil or the minerals it contains, which may not in the least dis- 

 order the water, and yet be of very important benefit. These can 



