F “hits? 
Sor the Advancement a: Science. . 
have compared the resistance of a eenabadl 4 legraphie ren with the 
of an entirely metallic. es raat B a lengthvof wire twice as 
great as that employed. in a mixed c Thave also! formed metallic 
circuits of very fine biznes: ‘wires, heii the. same ‘Tesistance at . 
that of a mixed circuit, in which the:metallic portion remained*con- _ 3 
stantly the same, and to which were added different lengths of ebrths sos 
The following are the principal conclusions drawn from experiments 
sco a 
——according to the specific gravity of that earth ,——according to its depth 
beneath the surface,—according to the nature of the electrodes and ex- 
tent of their surface. This resistance,does not increase with the ins. 
ear a cae see sam youre power; different portions of the 
a eo the: vlodiiadeh we may find og an increase or diminution in 
the resistance of the earth. Likew in operating ona long mixed 
telegraphic circuit, which is not petfectly isolated, owing to the effect 
sof the different derived circuits formed between the posts ‘and the earth, 
electric current is stronger near the piles than at a distance, and 
s 
results which I had obtained from my former bm experiments. 
The resistance of a layer of earth appears to diminish as its: length in- 
creases only in cases where we meet with other layers of better conduct- 
ing power. In every layer of earth of a certain constant a 
power, the resistance which at first increases very feebly with the in 
creased length of the layer. , becomes 
same for all the spp lengths, however great, on which experiments 
have been made. Now, it is evident that as the increase of resistance 
ina long eg circuit i is ey perceptible when we add to the 
circuit, by means of two e electrodes, a thin stratum of water; so 
we ought to find j in the ae pion telegraphic circuits that the resist- 
ance of the earth is rig or ‘pearly sO, since it is equal to that of a thin. 
stratum of water of a very large section. The law of the conducting 
_ power of the’ earth edad established, it remains to give the theory of 
his phenomenon. ‘The opinion of the scientific world is divided on 
point. Some explain the good counleesitg power of the earth by 
the almost Shake. section of the earth compared with the distance of 
