156 Boyal Society : — 



1 1 



battery of ten or twenty times as many cells for a time Jq « "i" 20'^' 



If I were to guess what might be caUed " the retardation," which 



in the observations between Greenwich and Brussels was found to 

 be about ^0^^ of ^ second, I should say it corresponded to four or 

 five times n, but this must depend on the kind of instrument used, 



