372 



Sir W. Thomson. Harmonic Analyzer. [May 9, 



One long wooden rod, properly supported and guided, and worked 

 by a rack and pinion, carries five forks to move the five globes and a 

 pointer to trace the curve on the paper cylinder. The shaft of the 

 paper cylinder carries at its two ends cranks at right angles to one 

 another ; and a toothed wheel which turns a parallel shaft, and a third 

 shaft in line with the first, by means of three other toothed wheels. This 

 third shaft carries at its two ends two cranks at right angles to one 

 another. 



Another toothed wheel on the shaft of the paper drum turns 

 another parallel shaft, which, by a slightly oblique toothed wheel 

 working on a crown wheel with slightly oblique teeth, turns one of 

 the five disks uniformly (supposing to avoid circumlocution the 

 paper drum to be turning uniformly). The cylinder of the integrator, 

 of which this one is the disk, gives the continuously growing value of 

 fydx. 



Each of the four cranks gives a simple harmonic angular motion to 

 one of the other four disks by means of a slide and crosshead, carrying 

 a rack which works a sector attached to the disk. Hence, the cylinders 

 moved by the disks, driven by the first mentioned pair of cranks, give 

 the continuously growing values of 



(2ttXj -j f • 2irx j 

 y cos ax, and y sin ax ; 

 c J c 



where c denotes the circumference of the paper drum : and the two 

 remaining cylinders give 



