r: • > • ) 

 f).).) 



first measurement of the field-intensity the bahance was moved along 

 the field over a distance of 1.24 m.ni , this being one revolution of 

 the niierometer-screw of the sliding support. The average intensity 

 was measured again, and after ea<'li measurement the biilance was 

 moved along the field ovei' tlie same distance, till at last the 

 balance had passed through the entire field, and had come out of 

 the interferi-icum. 



In this series of experiments I found that the greater part of the 

 field might be called absolutely homogeneous. Proceeding from this 

 part the average intensity could now be calculated for each distance 

 of 1.24 mm. Obviously the figures calculated for the weaker part 

 of the field cannot l)e regarded as very accuiate. By graphical inter- 

 polation I got figures which seemed to me to be more conform to 

 the real value. In order to prove this, I recalculated from the values, 

 for each part of 1,24 mm., average values over 19.05 mm. In 

 table I we find in colunin 1 the calculated values for each part of 

 the field of 1.24 mm. length. The second column gives the recal- 

 culated figures for each length of 19.05 mm., whilst in the 3^'^'coUimn 

 the figures as measured are given. The degree of agreement between 

 the 2"^^ and the 3''^ column indicates the degree of accuracy between 

 the same. In general this correspondence is not unsatisfactory, only 

 the values 2 and 3 show difïerences of 2 7« and 3.5 "/o- For the 

 rest the difference amounts to less than 1 " g. The curves of fig. 7 

 represent graphically the numbers given in the table. 



With the figures obtained for the local intensity of field we can 

 now draw the exact shape of the string, by means of the graphical 

 construction described in the beginning, or we can calculate it. The 

 calculation is made by two additions that serve as means of integra- 

 tion. The first addition produces the series of figures 0, O-}-!, 

 0-[- 1 -f- 2, 0+ 1 + 2 -f 3 etc., consequently the values 0, 3600, 

 7250, 11050 etc., which indicate the integral values of the lateral 

 pressure, at each point. 



If these values be a, b, c, d, then a second addition in exactly 

 the same way, gives us; a, a -\- h, a -\- h -\- c, a -\- h -\- c -\- d, etc. 

 These last figures are given in column IV and show the relative 

 deviation with regard to a }"-axis tangential to the point of maximal 

 amplitude. They enable us to calculate with the field-current employed 

 the relatively maximal deflections of any part of the string. 



If e.g. the maximal deflection of a string of a length of 2 X 48 

 parts of 1.24 mm. each v/ith a given current were 191.8, then the 

 deflection with the same current would be 41.5 for a string of the 

 same material and tension, but only half the length. We see that in 



