85 



This was eqval to the difference between the two devia- 

 tions obtained by connexion ot P n with the earth-plate Z n i or 

 Pn — Z„i and of Pi with Z nI or Pi — Z n i; that is to say 



Pn — Pi = Pn — Z n i — (Pi — Z n i) 



The same result was obtained by means of an other 

 earth-plate Z nn . 



Out of these experiments, repeated several times, it 

 goes forward that P n — Z„i — (Pi — Z n i) (or Z nn ) give a mea- 

 sure of the EMF between the both point-apparatus and that 

 the above mentioned corrections are insignificant. 



Though a nearer studie of the properfcies of the point- 

 apparatus was much aggravated by the incessant variations, 

 the following result with high degree of probability: 



a) The circuit, consisting of the point-apparatus, the 

 galvanometer and the earth-plate united with wires, all well 

 insulated, behaves as a metallic circuit viz. composed ot 

 conductors. As the principal part of the resistance of the 

 circuit lies in the point-apparatus itself, it is natural that 

 the resistance varies with the extern al circumstances in the 

 atmosphere, the pressure, the moisture etc. 



b) Two identic point-apparatus, at the same height in 

 the atmosphere and communicating trough a galvanometer, 

 will give zero or annul the effect of each-other. 



c) The effect of two or several point-apparatus, even 

 at. different height, equal the sum of the effects of the dif- 

 ferent apparatus. 



d) The galvanic resistance of such an apparatus can 

 be measured in the ordinary way. As the varations are 

 very numerous the measurement must be made with two 

 sensible galvanometers as identical as possible, whereby 

 one is used for the observations of the variations, the other 

 for measure of the resistance. In this vay it will be pos- 

 sible to reduce them all to a common or normal-stand. 



é) The galvanic resistance r in the circuit, consisting 

 of two point-apparatus, united trough the galvanometer, is 



