410 C. A. Chant — Reception of Electric Waves. 



wire. If we consider the connection from a to i^to be equiv- 

 alent to 200 cms , the above determination would make the con- 

 denser equal to 40 cms of the wire. 



It will be observed in Table II that the minimum for wires 

 of lengths 4, 5 and 6 meters is at the middle of the wire, or the 

 wire is vibrating in its own fundamental mode, while with 

 wires 8 to 11 meters long the minimum is about 210 cms from 

 the free end, approximately as in Table 1 and almost certainly 

 due to the same cause. 



This would indicate that in the case of the longer wires the 

 oscillation is forced on the wire, in the case of the shorter the 

 oscillation is that natural to the wires themselves. 



2. Examination, by the Method of Resonance, of the Radiation 

 from the Rraun, Slaby-Arco and (Simple Marconi Trans- 

 mitters. 



In these experiments the transmitter was arranged as usual, 

 and the receiving wire, as in the preceding experiments, was 

 stretched parallel to the transmitting antenna. The action of 

 the incident waves was measured by hanging the detector on 

 the end of the wire. To begin with, the wire was of consid- 

 erable length, and it was gradually shortened, 10 or 20 cms at a 

 time, the effect on the detector hung on the end being observed 

 for each length. As the length of the wire approached that 

 for resonance with the transmitted waves the readings rose, but 

 as the resonant length was passed they fell, until at last the 

 wire was so short that the effect was hardly observable. From 

 the curve obtained by plotting lengths of receiving wire as 

 abscissas and amount of demagnetization (measured by the 

 magnetometer readings) as ordinates, the length of wire which 

 gave maximum effect was easily determined. This method of 

 determining resonant lengths is extremely simple and easy of 

 application. 



The Braun transmitter was the one used in the experiments 

 just described, the antennae being 3 and 4 meters long. The 

 Slaby-Arco transmitter was that form of Brawn's directly-con- 

 nected system described in the former paper. In the simple 

 Marconi radiator the transmitting antenna was joined imme- 

 diately to the binding-post forming one terminal of the sec- 

 ondary of the induction coil ; the other binding-post was joined 

 directly to earth, while the spark-gap was between knobs 19 mra 

 in diameter on the ends of rods passing through the binding- 

 posts. The distance between these posts was 22 C1US , and the 

 earth-connection was 25 cms long, i. e., the distance to earth 

 from the end of the wire attached for antenna was 47 cms . 



The results obtained are shown in Table III and the curves 

 of figures 5 and 6. The experimental arrangement seems 

 simple and unequivocal, but the conclusions to be drawn are 

 not all so. 



