182 POPULAR LECTURES AND ADDRESSES. 



moved. His left hand he turns always in one 

 direction, and at as nearly constant a speed as is 

 convenient to allow his right hand, alternately in 

 contrary directions, to trace exactly with the steel 

 pointer the tidal curve on the paper, which is 

 carried across the line of to-and-fro motion of the 

 pointer by the revolution of the paper drum, of 

 which the speed is in simple proportion to the 

 speed of the operator's left hand. 



The eleven little counters of the cylinders in 

 front of the disks are to be set each at zero at the 

 commencement of an operation, and to be read off 

 from time to time during the operation, so as to 

 give the value of the eleven integrals for as many 

 particular values of the time as it is desired to have 

 them. 



A first working model harmonic analyser, which 

 served for model and for the meteorological analyser, 

 now at work in the Meteorological Office, is here 

 before you. It has five disk-globe-and-cylinders, 

 and shafting geared for the ratio I : 2. Thus it 

 serves to determine, from the deviation curve, the 

 celebrated "ABCDE"of the Admiralty Com- 



