S/X WII^LIAM SIEMENS, F.R.S. 



373 



the influence of this disturbing cause upon the instrument should 

 be accurately ascertained in order that allowance may be made for 

 latitude in its ordinary use. In order to test separately the eflect 

 of latitude upon the instrument, its indications were taken on the 

 8th of December at Westminster, lat. 51 81' N., long. 0" 7' W., 

 and afterwards at Brighton, lat. 50 50' N., long. 0" 10' W., which 

 is nearly due south of Westminster 41 nautical miles. At West- 

 minster the indications were 



fathometer. 



2 turns 432 

 431 

 430 



Barometer. 



30-425 

 30-425 

 30-425 



Thermometer. 



"Fahr. 



43-4 



43-6 

 43-4 



These readings were taken at intervals of 5 minutes. The 

 instrument was then carefully packed and removed to Brighton, 

 where it was again set up. The first reading was taken an hour 

 after arrival, and the readings taken during the afternoon are 

 noted below. 



The readings of the instrument taken the next morning at 



Westminster were 



2 turns 440 

 439-5 

 440 



30-42 

 80-42 

 80-42 



48 



::;-_'. 



48-2 



It will be found that, on correction being made for variation of 

 temperature and atmospheric density, and taking the mean of the 



