36 U. S. COAST AND GEODETIC SURVEY 



Unless previous tide observations have been taken in the locality the 

 value for H must be estimated. From best information available 

 ascertain the approximate heights reached by the highest and lowest 

 tides and then note the height of the water surface at the time of 

 installation as compared with a plane midway between the estimated 

 highest and lowest, taking H as positive if the surface is above mid- 

 extreme level and negative if below this level. 



93. Before installing the float it is a good plan to pass several loose 

 loops of wire through the supporting ring to aid in its recovery from 

 the float well if the float wire becomes accidentally broken. Next, 

 taking a spool of wire, attach one end of wire to the float and lower 

 it into the well until it comes to rest on the surface of water or kero- 

 sene. Lead the wire to the float drum of the gage and, after measur- 

 ing off an additional distance equal to L as determined from the 

 formula in the preceding paragraph, cut the wire from the spool and 

 attach the end of the wire to the float drum by passing it through a 

 small hole near the outer edge and knotting it. 



94. If the gage is of the latest type, with removable pencil screw, 

 wind up the float wire by turning the float drum on its shaft until all 

 threads on the drum are filled or until the float has reached its upper 

 limit of motion. When doing this the counterpoise drum is left un- 

 disturbed with the counterpoise hanging close to the floor. Both drums 

 are then secured rigidly to the drum shaft by tightening the capstan 

 lock nuts on the two sides. The float is then allowed to descend 

 slowly until it rests lipon the surface of the water in the well. As the 

 float descends it automatically winds up* the counterpoise wire on its 

 drum. The pencil screw may now be replaced on the gage with the 

 pencil arm set to bring the record curve near the middle of the paj)er, 

 consideration being given to the present stage of the tide in its relation 

 to the mid-extreme tide. 



94a. The following instructions apply only to the old type gage 

 without removable pencil screw. Having determined the proper 

 length of wire in accordance with paragraphs 92?-93, remove the float 

 drum entirely from the gage and wind the float wire upon it, raising 

 the float as necessary, until all the threads on the surface of the drum 

 are filled or until the float has reached its upper limit of motion. Re- 

 place the drum on the gage and secure it with the two clamping nuts 

 provided for the purpose, but holding it carefully against the sudden 

 falling of the float. Next, holding the pencil arm to one side to keep 

 it from immediately engaging the threads of the pencil screw, allow 

 the float to descend slowly. With a gage equipped with a pencil 

 screw of 1-inch pitch, release the pencil arm after 2^4 turns if the 

 drum is 1% inches wide, or after 7^ turns if the dnmi is 1% inches 

 wide. With the pencil screw of %-inch pitch, release the pencil arm 

 immediately for the drum 1% inches wide or after 1^/2 turns for the 

 drum 1% inches wide. After the release of the pencil arm let the 

 float continue to descend slowly until it rests upon the water or kero- 

 sene in the well. The lowering of the float automatically winds up 

 the counterpoise wire and moves the pencil arm approximately to its 

 correct position. If any further adjustment of the position of the 

 pencil arm is necessary, it may be accomplished by loosening the 

 clamping nuts holding the float drum and turning the pencil screw 



