C 8r ] 
every Part thereof is in a great degree non electric; 
fo here the whole Quantity, or nearly fo -f , deter- 
mined that Way, was felt by the Obfervers at the 
nine Mile-Stone; whilft thofc at the other Station 
felt fo much of their Quantity only, as did not go 
through the Vegetables; that is, that Proportion only 
in which Iron is a greater Non-eledric than the 
Vegetables. 
Tho' the eledrical Commotions, felt by the Ob- 
fervers near the feven Mile-Stone, were not ftrong^ 
they were equally conclufive in (hewing the Differ 
cnce between the refpedive Velocities of Elc&ricity 
and Sound. 
The Space through which Sound is propagated 
in a given Time, has been very differently eftimated 
by the Authors, who have wrote concerning this 
Subjed. Roberval gives it at the Rate of y6o Feet 
in a Second; GaJJendus , at 1473 ; Merjenne at 
1474 ; Hu Hamel , in the Hiftory of the Academy 
of Sciences at Baris, at 1172; the Academy del 
Cimento, at 1 i8y ; Boyle at 1 200 ; Roberts at 1300; 
fValker at 1338; Sir Ifaac Newton at 968; Dr. 
Herham , in whofe Meafure Mr. Flamfteed and 
Dr. Halley acquiefccd, at 1142. But by the Ac- 
counts fince publifiied by M. GaJJini de Thury in the 
Memoirs of the Royal Academy of Sciences at 
Baris for the Year 1738. where Cannon were fired 
at various as well as great Diftances, under greaf 
Variety of Weather, Wind, and other Circum fiances, 
and 
4 The Author of this Paper, from a great Variety of Experiment*, 
is of Opinion ; that in this and the like Difpofitions of the Apparatus, 
the electrical Power, accumulated in the Matter contained in the coated 
Phial, is directed upon the Explofion thereof towards both Obfervers at 
the fame Inftant. 
L 
