196 IRRIGATION. 



answer every purpose for light and not very accurate work. 

 A very portable and convenient level, small enough to be 

 carried in the coat pocket, has been found by the author 

 of very great use in making preliminary surveys. It is 

 known as Locke's hand -level, and is shown in fig. 83. 

 Very accurate levels may be taken by using this instru- 

 ment in the following manner. A rod is provided, hav- 

 ing a blunt foot, that will rest upon the ground, and not 

 sink in soft soil, and of such a graduated length that it 

 will reach comfortably to a hight equal to that of the 

 eye of the person using it. The top of this resting rod 

 is slightly notched, so that the level will rest easily upon 

 it. By having the sighting rod marked at exactly the 

 same length from the foot as that of the resting rod, and 

 gauged up and down from this mark, (which should be an 



Fig. 83. LOCKE'S HAUD-LEVEL. 



0), the variations from the level may be taken with the 

 greatest readiness, and with sufficient accuracy for pre- 

 liminary work, or for a survey, where complete exactitude 

 is not required. Any slight errors that may be made will 

 balance each other, and in the aggregate there will be very 

 little variation from a true level in a line of some miles 

 in length. In the illustration the side of the level is 

 represented as broken away, to show the mirror in the 

 interior which reflects the bubble and the cross-bar in the 

 center. The bubble is seen at the top of the level. 



The Architect's level, fig. 84, made by W. &L. E. Gur- 

 ley, of Troy, N. Y. , is a more costly and complete level, 

 but a very simple, compact, and serviceable one. It has 

 a telescope 11 inches long, with the usual cross wires, 

 with adjustment of eye and object tubes. It may be 

 mounted on a Jacob-staff, or a tripod ; but for sighting 



