310 



THE IRKIGATION AGE. 



BOSTROM'S IMPROVED FARM LEVELS AND 

 BUILDERS' LEVELS. 



This instrument is of simple and compact con- 

 struction, possessing advantages which render them of 

 special value to farmers, builders and railroad contrac- 

 tors for laying out irrigation ditches and laterals, con- 

 structing coffer dams and head works for main ditches, 

 ascertaining the heights of springs and waterfalls and 



A 



connected with the plate supporting the turret by a 

 spring detained screw c, giving it in effect a ball and 

 socket joint. Only three leveling screws are used, 

 which simplifies the manipulating, allowing the tele- 

 scope to be adjusted with the least loss of time. The 

 leveling of the plate to a perfectly horizontal position 

 is done in two adjustments. The first is made with the 

 spirit level parallel with two of the leveling screws, 

 these being turned in opposite directions until the 



Fit. 2. -Cross Sections of Plane of the Telescope and the Spirit Level. 



for leveling foundations, floor timbers and sills, leveling 

 lines of shafting, setting machinery, etc. There has 

 long been felt the want of both a farm level and a 

 builder's level that should be practicable, accurate and 

 low priced, to take the place of the expensive and com- 

 plicated engineering instruments ordinarily used for 

 the purposes named above. 



The instrument as shown in Fig. 1 stands at about 

 the height of the ordinary surveying level and weighs 

 considerably less. It is easy of adjustment and is de- 

 signed for quick and accurate work, there being no long 

 and short back and front sights necessary in testing its 

 accviracy. The farm level is constructed of iron and the 

 builder's level entirely of brass, both have a graduated 

 scale divided into 360 degrees, numbered from zero to 

 90 degrees in both directions, giving zero points on 

 opposite sides of the circle. By a vertical line on the 

 side of the turret, angles may be read within a frac- 

 tion of a degree. The angle being adjusted, it is 

 clamped in position by a single clamping screw, shown 

 in Fig. 2, which represents a cross section of the instru- 

 ment in the plane of the telescope and spirit level. A 

 ground spirit level vial, shown at the right in Fig. 2. 

 is provided, which makes the instrument sensitive and 

 accurate. The telescope is acromatic and is designed 

 and made especially for this instrument. It gives a 

 clear field, and the magnifying power of the eye piece 

 is as great as can be used to advantage on an instm- 

 ment of this kind. The cross hairs are set in the eye 

 piece and are secure against displacement except through 

 extreme carelessness. A neat leveling rod is furnished 

 with the instrument, which is of light construction and 

 telescopes to 5 feet when closed, its extended length 

 being 9/4 feet. It has a sliding target and is gradu- 

 ated to feet, inches and fourths of an inch. When 

 desired, a compass is added to the builder's level, 

 whereby it can be used in retracing land lines or for 

 determining the bearing and direction of lines in pre- 

 liminary surveys, etc. The farm level is constructed 

 on the same lines as the builder's level, the body being 

 made of iron instead of brass and the clamping device 

 for the circle of degrees omitted. The construction of 

 these levels is unique and interesting and will be under- 

 stood by reference to Pig. 2. The adjusting head b 

 screws directly to the top of the tripod and is flexibly 



bubble is at the center. The turret is then turned at 

 right angles to its first position and the third screw 

 turned until the level is again horizontal. The upper 

 and lower faces of the turret proper are parallel, so that 

 it is reversible. The telescope passes through diamet- 

 rically opposite holes in the turret and may be adjusted 

 bv means of the screws d, to make certain its accurate 

 position. The testing consists of sighting on an object 

 through the telescope when it rests in its normal posi- 



Fig. 1 . Bostrom's Improved Builders' Level. 

 General View of Instrument ready for use. 



tion, as shown, and in sighting on the same object after 

 reversing the turret so that its former upper face be- 

 comes the face resting on the turret support. The 

 adjusting screws c are provided for correcting the level 

 if it is found to be out of adjustment. It may be easily 

 tested by leveling it and turning it end for end, when 

 the bubble should still be in the center. There is 

 seldom an occasion to correct these adjustments unless 

 the instrument has suffered some damage from a mis- 



