136 U. S. COAST AND GEODETIC SURVEY 
the operator has noted the time and height readings of the high or 
low water he may easily break the circuit at the crank hub by a slight 
inward pressure against the crank handle, thus releasing the arma- 
ture and pawl and permitting the machine to be turned forward to 
the next stop. By means of a small switch (23, fig. 24) just below the 
crank the circuit may be held open to prevent the automatic device 
from operating when so desired. 
390. Nonreversing ratchet—Upon the crank shaft, close to the bear- 
ing in the desk frame, there is a small ratchet wheel and above this 
there is a pawl (24, fig. 24) that is lifted away from the wheel by friction 
springs when the machine is being turned forward but which is 
instantly thrown into engagement when the crank is accidentally 
turned backward. By pushing in one of the small buttons (22, fig. 24) 
just above the crank the pawl is locked so that it cannot engage the 
ratchet, thus permitting the machine to be turned backward when 
desired. Pressure on another button releases the pawl. 
391. Tide curve.—-The tide curve which graphically represents the 
rise and fall of the predicted tide is automatically traced on a roll of 
‘paper by the machine at the same time that the results are being 
indicated on the dials. The curve is the resultant of a horizontal 
movement of the paper, corresponding to the passing of time, and a 
vertical movement of a fountain pen (18, fig. 23), corresponding to the 
rise and fall of the tide. The paper is 6 inches wide with about 380 
feet to the roll, which is sufficient to include a little more than a full 
year of record of the predicted tides at a station. The paper should 
be about 0.0024 inch thick in order that the complete roll may be of 
suitable size for use in the machine. 
392. Within the dial case, near the upper right-hand corner, is a 
mandrel (38, fig. 25), which can be quickly removed and replaced. It 
is designed to hold the blank roll of paper, the latter being wound upon 
a wooden core especially designed to fit on the mandrel. At the 
bottom of the mandrel is an adjustable friction device to provide 
tension on the paper. From the blank roll the paper is led over an 
idler roller (34, fig. 25), mounted in the front plate of the dial case, 
then across the face of the machine for a distance of about 13 inches 
to a feed roller (38, fig. 25), then over the feed roller to the receiving 
roller (36, fig. 25), upon which it is wound. 
393. The feed roller governs the motion of the paper across the face 
of the machine and is provided near each end with 12 fine needle points 
to prevent the paper from slipping. The feed roller is controlled 
by the main vertical shaft of the dial case through gearing of such 
ratio that the feed roller will turn at the same rate as the main 
vertical shaft; that is to say, one complete turn of the feed roller 
will represent 12 dial hours in time. The feed roller being 6 inches 
in circumference the paper will be moved forward at the rate of 
one-half inch to the dial hour. A ratchet and pawl (37, fig. 25) are 
so placed as to leave the paper at rest when the machine is turned 
backward. If desired, the paper feed can be thrown out of action 
altogether by turning a small milled head on the ratchet gear. 
394. To provide for the winding up of the paper on the receiving 
roller there is a sprocket wheel (38, fig. 25) held by adjustable friction 
to the upper end of the feed roller. Fitted to the top of the receiving 
roller is a smaller sprocket which is driven by a chain from the feed- 
roller sprocket. The ratio of the sprockets is such as to force the 
