240 PROCEEDINGS OF THE AMERICAN ACADEMY. 



period of the primary as 5 to 3. The side of the rectangle was 127.5 

 cm., and the end capacities equivalent to 62 cm. of wire. The half 

 wave length was 



30 + 127.5 X 2 + 62 X 2 =: 409. 409 -^ 255.6 = 1.6, nearly. 



This was the only indication observed of complexity in the vibra- 

 tion of the oscillator. It appears that, when the oscillator is especially 

 active, it can excite a circuit having this ratio to itself, or that the 

 vibration is not a simple one. Time was not at disposal sufficient to 

 decide this point, which is left for future investigation. 



A comparison of the curve (Fig. 1 of Plate) obtained from the plain 

 wire circuit with the curve (Fig. 3 of Plate) obtained when capaci- 

 ties were fixed on the free ends shows a quite satisfactory agreement 

 in the results, which tends to create confidence in both methods. The 

 half wave length by the first is 254.3 cm., by the second it is 255.6 cm., 

 values which differ by about one half of one per cent. There is 

 a marked difference, as was to be expected, in the form of the curve 

 for the quarter wave length next the free ends. When end capaci- 

 ties were used, the accumulation of charge seemed mainly confined 

 to those out of reach of the exploring terminals, while with the plain 

 wire it seemed distributed over a greater distance, and could be 

 detected by the exploring terminals. In each case the effect of the 

 ends was to make the curve depart from its normal form along the 

 free wire. 



An annealed iron wire (diameter 0.1186 cm.) was put in place of 

 the copper, and the same series of observations was made as with the 

 copper. The results are shown graphically in the lower curve of the 

 upper pair in Figure 4 of the Plate. The maxima E, F, G, H, appear 

 at 42.5, 301, 553, and 805 cm. ; in each case before the corresponding 

 maxima with the copper, and the difference increases with the length 

 of the circuits, as is evident from an examination of the curves. The 

 successive additions after the first maxima are 258.5, 252, and 252 

 cm. ; the last two agreeing, while tlie first, as with the copper, is 

 larger. With the sides of the rectangle fixed at 805 cm., the form of 

 the wave was found as shown in Figure 2 of the Plate, The third 

 minimum occurs at 740 cm. Calculating its half wavelength as before, 

 740 + 15 = 755. 755 ^ 3 = 251.6 cm. This agrees well with the 

 value 252 cm. given above by the last two additions, but differs by 

 4 cm. from the value found when the copper was used. 



The same series of observations was repeated with a second pair 

 of finer wires (diameter of copper wire 0.07836 cm., diameter of iron 



