152 



GARDEN MANAGEMENT. 



358. For levelling extensive tracts of country for railways, canals, &c., a 

 theodolite, which is a spirit-level raised on three legs, and furnished with a 

 telescope, is the instrument employed. A quadrant is also frequently used 

 for the same purpose, and for determining the level of drains, &c. The follow- 

 ing diagram and remarks are taken from Loudon's "Self-Instruction for 



Young Gardeners," the last 

 contribution of that great 

 and good man to a science 

 that he loved better than his 

 life : — " Suppose it were re- 

 qmred to run a level through 

 the ground indicated, AB, 

 from the point A. Provide 

 a few staves proportioned 

 in length to the work in hand, and let them have cross-pieces to slide 

 up and down ; then, having firmly fixed the staff in the ground, to which 

 the quadrant is attached at the point A, set the instrument in such a 

 position that the plumb-line shall hang exactly parallel to the pei-pendicular 

 limb of the quadi-ant ; the upper limb will then be horizontal. This done, 

 direct the eye through the sights, and, at the same time, let an assistant 

 adjust the slides on each staff so as exactly to range with the line of vision. 

 Then suppose the height AC to be 5 feet downwards from the upper side of 

 the slide upon each staff, so shall the dotted line AB represent the level 

 line required. Suppose the operation had been to determine a cut for a drain, 

 to have a fall of 3 inches in every 20 feet, the distance between each staff in 

 the above figure may be supposed to be 20 feet, then 5 feet 3 inches would 

 have to be measured down the first staff, 5 feet 6 inches down the second, 

 5 feet 9 inches down the third, &c, &c. The dotted line AB would then 

 represent the line parallel to the bottom of the intended drain." 



359- Where hills or mounds are to be thrown up, stakes should be inserted 



of the desired height, and a 

 line stretched across their 

 tops to show the conforma- 

 tion of the surface, as in the 

 cut. These stakes, in all gar- 

 den operations, should range 

 from 10 to 20 feet apart, 

 15 being a good average ; they are not only necessary for ascertaining the 

 levels, but enable the men to perform their work with the utmost ease and 

 certainty as to the result. 



360. One of the chief things to be attended to in levelling, is to retain all 

 the best soU for the surface : this increases the labour and expense, but is of 

 the first importance in all garden operations. However, if judgment is 

 exercised in the performance of the work, the sui'face-soil can generally bo 

 passed over on to the new level without the intervention of carts or barrows. 



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