724 Experiments on the communication of QSept. 



In this cursory description I confine myself to facts alone, and 

 refrain from entering on any theoretical speculation as to the causes 

 of these singular and deeply interesting phenomena. 



Experiments with the Electro-magnet No. 1. 

 The day being fine, the ground and bamboos perfectly dry, at 

 9. a. m. the sustaining power of the electro-magnet No. 1. was tested 

 with iron conducting wires ten feet long, and found to amount to 46 lbs. 

 With one mile of same wire, ^ mile at each side, 

 it supported, . . • • . . 18 lbs. 



2 Miles of wire, . . . . . . 8 lbs. with difficulty. 



3 Miles of wire, 2^ lbs. 



4 Miles of wire, . . . . . . 23 ounces, with difficulty. 



4J Miles, .. .. .. sustaining force ceased altogether. 



Electro-magnet No. 2. 



With 10 feet wire, 12 lbs. 



1 Mile, 7 lbs. 



2 Miles, 3 lbs. 



3 Miles, . . . . . . . . 0| lb. 



4 Miles, . . . . . . . . no sustaining power. 



Assuming iron to be inferior to copper in about the proportion of 1 to 7, 



according to Sir Humphry Davy and Becquerel's standard of conductors, 

 this experiment shews that for equal diameters of wire, copper would 

 convey the signal by Henry's method to about twenty-one miles in an 

 imperceptible period of time. This distance might be extended by en- 

 larging the diameter of the wires, but to what limit, is as yet unknown. 



Experiments with Galvanometer. 



The astatic galvanometer was arranged and levelled with much 

 care, the needles retaining a very slight degree of directive force so as 

 to cause them to swing in the magnetic meridian. 



At 1 Mile, deviation maximum or . . . . 90° 

 The needles being restrained by pins at the quadrant : — 



At 2 Miles. 90° 



— 3 Miles. 75° 



— 4 Miles. 63° 



— 6 Miles. 40° 



— 10 Miles. .. .. , .. 11° 



— 11 A Miles at each side to total cir- 1 , , ,.,, 



cuit23 miles. f barely perceptible. 



