312 



KELVIN 



with another of 423. All the other wheels have compara- 

 tively small numbers of teeth. The machine is finished 

 now, except a cast-iron sole and cast-iron back. A fly- 

 wheel of great inertia enables me to turn the machine fast, 

 without jerking the pulleys, and so to run off a year's curve 

 in about twenty-five minutes. This machine is arranged for 

 fifteen constituents in all and besides that there is an ar- 

 rangement for analysing out the long period tides. 



The following table shows how close an approximation to 

 astronomical accuracy is given by the numbers chosen for 

 the teeth of the several wheels. These numbers I have found 

 by the ordinary arithmetical progress of converging frac- 

 tions. 



