MANUAL OF TIDE OBSERVATIONS 15 



from the time clock through the back of the clock case is a spindle 

 carrying a short arm (33, fig. 9) called the striker lifter. This is 

 actuated by a cam in the clock and operates the hour-marking device. 



25. Rollers. — There are three rollers on the gage, which are desig- 

 nated as the supply roller^ the main roller, and the receiving roller. 

 The supply roller (4, fig. 4) is a solid rod on which the blank roll of 

 paper is placed. When installing a new roll of paper, this rod may 

 be readily removed from the gage and passed through the hole in 

 the center of the blank roll. When on the gage it is held in place by 

 guide springs (5) at each end. These springs also press against the 

 ends of the roll of paper to keep it from unwinding too fast and 

 thus hold the paper taut as it is fed over the main roller. The pressure 

 exerted by these springs may be regulated by slightly bending them. 



26. The main roller (14, fig. 5) is a hollow cylinder 13l^ inches 

 long and 12 inches in circumference. Near each end of the cylinder 

 sharp steel pins are set at 1-inch intervals to keep the record paper 

 from slipping. Attached to the axis of the cylinder at one end there 

 is a hinged carrier arm (34, fig. 6) which engages the carrier wheel 

 geared to the motor clock. Through this connection the main roller 

 is rotated at the approximate rate of one turn in 12 hours, thus feeding 

 the paper forward at the rate of 1 inch per hour. 



27. The receiving roller (17, fig. 5), which is designed to receive 

 the completed record, consists of a solid core with one side flattened 

 and an outer shell in which a slit runs the entire length. With the 

 slit opposite the flattened side of the core, the end of the paper is 

 inserted and then secured in place by a slight turn of the shell. The 

 roller is held in place in its bearings by two pins which may be 

 released by pressure on buttons (18) near the ends of the roller. At 

 one end of the roller there is a small drum ( 16) known as the tension 

 weight dnirti, upon which is wound a cord attached to a weight which 

 serves to wind up the record paper on the receiving roller. The drum 

 is arranged so that it can be turned independently of the receiving 

 roller when winding up the weight. In some of the instruments this 

 is accomplished by a pawl and ratchet, while in other instruments the 

 loosening of a lock nut enables the drum to be moved aside, thus 

 disengaging it from the roller itself. 



28. Record paper. — The paper for the standard automatic tide 

 gage is furnished in rolls about 13 inches wide and containing ap- 

 proximately 66 feet in length, which is sufficient for 1 month of 

 record. The paper is plain without any ruling. After the tide curve 

 has been traced upon the tide roll the record is called a marigram. 



29. Pencil screw. — The pencil screw (6, fig. 4) is a rod about 

 % inch in diameter with a square screw thread with a 1-inch pitch, 

 except that for a very large range of tide a screw with a 14 -inch pitch 

 is used. The pencil screw is rotated through the action of the float 

 as the tide rises and falls, and in turn actuates the pencil arm causing 

 a pencil to trace the record. The threads at each end of the pencil 

 screw are turned down to prevent the pencil arm from jamming on 

 reaching the extreme limits of the rod, and springs (7, figs. 7 and 9) 

 are provided at each end to return the arm to the threaded portion of 

 the screw as soon as the tide reverses. In the latest type of instru- 

 ment the pencil screw may be removed from the gage for cleaning 

 without disturbing the wirine to float or counterpoise. At one end 



