° Se SRS = = B- = a 
oY) ose slitanlinceaneemiiet. _ us a amet * _ | 
C. Abbe on the Repsold Portable Circle. 209 
westward of the survey of the lakes, or rather the completion 
of the labors of N. W. boundary survey should lead to the deter- 
mination of an arc of 55 to egrees of longitude—the largest 
necessary in determinations of longitude, that not only the obser- 
vers be exchanged, but also with them their transits, their relay 
batteries, chronometers and chronographs, and all apparatus used 
at either en 
sa! 
five to twenty-five days five, ten, twenty secondary stations, and 
returning to the same or another primary station, will be 
the relative position of all the secondary points 
