Wow. Below are some 1899 article illustrations, some of which depict the
ion-path "virtual antennas" created by Tesla's x-ray beam devices:
Nikola Tesla holding in his hands balls of flame
http://homepage.ntlworld.com/forgottenfutures/tesla/tesla_2.gif
Tesla's propsed arrangement of balloon stations for transmitting
electricity without wires
http://homepage.ntlworld.com/forgottenfutures/tesla/tesla_1.gif
All illustrations
http://homepage.ntlworld.com/forgottenfutures/tesla/tesla_nx.htm
Article: The New Wizard of the West, May 1899 C. McGovern
http://homepage.ntlworld.com/forgottenfutures/tesla/tesla.htm
I wonder if the drawing of the "balls of flame" was done live from an
actual demo, or from a verbal description given to the artist? The
equipment in the backgrounds of these illustrations looks like it was
drawn from life. Most probably these are carbon-button lamps run via
e-field coupling, and not "BL."