70 



MR. RUMKER'S OBSERVATIONS 



consequently stationary ; the change of altitude was then proportional to the 

 change of time, and the calculated hour-angle did not require the troublesome 

 reduction of the middle of times to the middle of altitudes. 



Though it cannot be expected that absolute altitudes will give the right 

 ascensions with the same consistency amongst themselves as observations with 

 a transit instrument, the mean of a great number of them derived from obser- 

 vations made on both sides of the meridian is more likely to be free from any 

 constant errors to which the transit instrument may be subject. 



