LONGITUDE OF McGILL OBSEEVATOEY. 



175 



Table VII, below, coutaius the resvilts of the star transit signals on June 23rd. Under 

 T is given the clock-face times of transit of the mean wires, as recorded on the chrono- 

 graphs. The next three columns contain respectively the corrections for level, azimuth 

 and collimation. Under R-M are the reductions of my observations to Prof. Rogers as 

 the normal observer. Column H contains a correction for the transmission and armature 

 time (see Table YIII) ; column M, the corrected times of meridian passages ; and the last 

 column the differences between these quantities, which is a measure of the difference in 

 longitude of the stations. 



In Table VIII, the column Z), and D, contains the mean results of the clock com- 

 parisons from Table VI, while J (D^ + D^ gives the difference of longitude, uncorrected 

 for personal equation, resulting from each night's work. The corrections for personal 



equation have been obtained from the values for Pi,-M = .130 sec*<î, and = .154 secirf, and 

 represent the average of R-M for all the stars observed by me on each of the nights. By 

 applying these quantities to those in the previous column, my clock corrections are reduced 

 to those of Prof. Rogers, whose absolute equation is known to be near zero. The column 

 JA therefore contains the difference of longitude obtained on each night. The combining 



