THE TIDES. 181 



seen in front respectively on the left and right of 

 the centre. The two other longer idle shafts for 

 the K and the P tides are behind, and therefore 

 not seen. That for the P tide serves also for the 

 simple integrator on the extreme right. 



The large hollow square brass bar, stretching 

 from end to end along the top of the instrument, 

 and carrying the eleven forks rigidly attached to 

 it, projecting downwards, is moved to and fro 

 through the requisite range by a rack and pinion, 

 worked by a handle and crank in front above the 

 paper cylinder, a little to the right of its centre. 

 Each of these eleven forks moves one of the 

 eleven globes of the eleven disk-globe-and-cylinder 

 integrators of which the machine is composed. 

 The other handle and crank in front, lower down 

 and a little to the left of the centre, drives by a 

 worm, at a conveniently slow speed, the solar 

 shaft, and through it, and the four idle shafts, the 

 four other tidal shafts. 



To work the machine the operator turns with 

 his left hand the driving crank, and with his right 

 hand the tracing crank, by which the fork-bar is 



