THE TRANSCONTINENTAL ARC. 221 
States engineers. Here is an instance where two organiza¬ 
tions, working independently, at different times, with dissim¬ 
ilar instruments, could find no appreciable difference in 
their results after their bases had been carried 110 miles by 
triangulation. This is even more remarkable than the cele¬ 
brated work of the Spaniards on the plains of Madridejos, 
where the probable error of their base-line is given as ap¬ 
proximately 5 - 00 W 0 T part. The perfect coincidence, how¬ 
ever, of the two bases cited above must be regarded as purely 
accidental. 
31—Bull. Phil. Soe., Wash., Vol. 13. 
