﻿588 Prof. J, A. Fleming on the Electric 



o 



recent improvements which have been made may not be out 

 of place. Thanks to the skill and ingenuity of Mr. F. E. Ives, 

 and his son Mr. H. E. Ives, the finished pictures are now 

 quite as good as the pictures shown by the Ives Kromoscope : 

 in fact it seems to me that they are perhaps a little better, 

 if that be possible. Three gratings are used as before, but 

 in the finished picture the mixed colours are made by juxta- 

 posed gratings instead of by superposed gratings, as originally. 

 This is a great advantage, for, as I showed some years ago, 

 superposed gratings show spectra of spectra which may be 

 very troublesome. A full description of the details of the 

 process, which has been most successfully worked out by 

 Mr. Ives, will be found elsewhere *. The pictures are as 

 " structureless " as those shown in the kromoscope, and can 

 be made much brighter if desired. The number of linear 

 elements has now been increased to 400 to the inch, which 

 makes them absolutely invisible. Mr. F. E. Ives has de- 

 signed a simple and compact viewing instrument, which is 

 placed before a well-lighted window, instead of being pointed 

 at a lamp in a dark room. By the very ingenious device of 

 employing four parallel slits suitably disposed, he utilizes the 

 light of the first two orders of spectra on each side. Thus 

 finished pictures are duplicated ad infinitum by a purely 

 mechanical process. 



LXIX. On the Electric Radiation from Bent Antennae. By 

 J. A. Fleming, ALA., D.Sc, F.B.S., Professor of Electrical 

 Engineering in University College, London f. 

 [Plates XVII. & XVIII.] 



IN March 1906, Mr. Marconi described in a Paper presented 

 to the Royal Society his inventions and interesting investi- 

 gations with wireless telegraph antennae consisting partly of 

 vertical and partly of horizontal wires for the purposes of 

 directive electric-wave telegraphy. At the conclusion he 

 says J:— 



" I have found the results (i. <?., the unsymmetrical radiation 

 and reception) to be well marked for wave-lengths of 150 

 metres and over, but have not been able to obtain as well 

 defined results when employing much shorter waves, the 

 effect following some law I have not had time to investigate." 



At the same meeting the present writer gave a brief 



* H. E. Ives, Phys. Rev. July 1906. 



t Communicated by the Physical Society: read November 23rd, 1906. 



J See G. Marconi, "On Methods whereby the Radiation of Electric 

 Waves may be mainly confined to certain Directions, and whereby the 

 receptivity of a Receiver may be restricted to Electric Waves emanating- 

 from certain Directions," Proc. Roy. Soc. Lond. A. vol. lxxvii.p.413,1906. 



