308 



KELVIN 



mittee, and is now regularly at work at their office har- 

 monically analysing the results of meteorological observa- 

 tions, under the superintendence of Mr. R. H. Scott. 



FIG. 132 represents the tidal harmonic analyser, con- 

 structed under the author's direction, with the assistance 

 of a grant from the Government Grant Fund of the Royal 

 Society. The eleven cranks of this instrument are allotted 

 as follows: 



The general arrangement of the several parts may be 

 seen from FIG. 132. .The large circle at the back, 

 near the center, is merely a counter to count the days, 

 months, and years for four years, being the leap year 

 period. It is driven by a worm carried on an intermediate 

 shaft, with a toothed wheel geared on another on the 

 solar shaft. In front of the centre is the paper drum, 

 which is on the solar shaft, and goes round in the period 

 corresponding to twelve mean solar hours. On the ex- 

 treme left, the first pair of disks, with globes and cylinders, 

 and crank shafts with cranks at right angles between 

 them, driving their two cross-heads, corresponds to the Ki, or 

 luni-solar diurnal tide. The next pair of disk-globe-and- 

 cylinders corresponds to M, or the mean lunar semi-diurnal 

 tide, the chief of all the tides. The next pair lie on the 

 two sides of the main shaft carrying the paper drum, and 

 correspond to S, the mean solar semi-diurnal tide. The 

 first pair on the right correspond to O, or the lunar 

 diurnal tide. The second pair on the right correspond to 



