81 



earth. We can regard the whole circuit from the point- 

 apparatus to the earth plate as a tubeshaped canal between 

 two great reservoirs of electricity, the atmosphere and the 

 earth and the current shows us which of them has abun- 

 dance and which has want of active matter. 



It will here be neeessary to answer the question: what 

 is the difference in the results obtained through the electro- 

 meter and through this method? With the eiectrometer we 

 are determinating the potential in a point p of the air, with 

 the point-apparatus we measure the EMF of a current from 

 the atmosphere to the earth. The electrometric measurements 

 can only in general give an idea of this force but does not 

 let us know what the value of the potential will be after 

 wards in the case that a little space surrounding the point 

 p should have been discharged; but the means to calculate 

 this value is given through the current in the circuit of the 

 point-apparatus and its wire to the earth. As it is not 

 electricity but the electrical current which is producing an 

 effect, we get in this method an improvement in the deter- 

 mination of the electrical forces in the atmosphere. 



The diagram fig. 8 shows the installation of the point- 

 apparatus in Kultala and gives a true idea of both appara- 

 tus which were used for the measurements. The results of 

 the observations must therefore give us numbers proportio- 

 nal to the existing EMF between the atmosphere and the 

 earth, whithin a certain area of its surface. It is however 

 not known how wide this area is and here we meet the 

 same difficulties as in the observations with the eiectro- 

 meter. 



By the passage of the electricity from the atmosphere 

 to the points generates a great resistance, as great that the 

 resisiance in the other part of the circuit signifies very little 

 in comparison with it. This resistance diminishes much 

 with the altitude in the atmosphere and here we have the 

 principal cause of placing the point-apparatus on the hig- 

 hest top of the mountain. The resistance will also dimi- 

 nish with the number of the points and if it would be pos- 



6 



