244 TELEGRAPHY ACROSS SPACE. 



Iii 1897, some further experiments were carried on by Professor 

 Slaby, of Charlotteuburg, on an even larger scale. He abandoned 

 every one of the novelties introduced by Marconi, and fell back upon 

 the methods previously known. He used a simple Lodge-Branly 

 coherer, employed elevated conductors as base lines, discarded the 

 useless little iron wire impedance coils in the local circuit, and substi- 

 tuted for the post-office polarized relay one made out of a Weston 

 galvanometer. His success shows that all that is essential can be thus 

 attained. He chose as the scene of his operations the Havel, and set 

 up elevated conductors upon the castle of the Pfaueninsel and on the 

 campanile of the church at Sacrow. Thus equipped, he transmitted 

 signals, at first about three-quarters of a mile, then 3 miles across the 

 water. He found trees and masts to interfere with the signals in some 

 degree. He then proceeded, with the aid of the military authorities, 

 to experiment over an open stretch of country — from Iiangsdorf to 

 Schonenberg. The elevated conductors were wires raised by means of 

 hydrogen balloons to heights of nearly 1,000 feet. Signals were 

 obtained at a distance of 21 kilometers, or over 13 miles. Neither in 

 Marconi's nor in Slaby's successful operations were syntonic devices 

 employed. 



The following table summarizes the results of Marconi's and Slaby's 

 work: 



Marconi : 



Flat Holm (seal 



Bream Down (sea) 



Spezia (land and sea) 



Spezia (open sea) 



Slaby: 



Sacrow (water and trees) 



Pfaueninsel (water and buildings) . 



Rangsdorf (land) 



Distance, 



Miles. 

 9 

 11 



3 

 134 



Base line. 



Feet. 

 150 



Ratio. 



100 



200(?)1 250(?) 

 100 I 200 



100 



200 

 950 



500 



70 

 50 

 70 



Commenting on these results, Slaby notes how over an open sea a 

 much* greater distance appears to be attained from a base line of given 

 length. Assuming Marconi's best proportion, he calculates the vertical 

 length of a base line needed for communicating across the English 

 Channel at Dover to be 265 feet, while from London to Paris, over land 

 and sea, would require 4,700 feet. He even estimates base' lines of 

 6,600 feet as sufficient, were it not for the curvature of the globe, to 

 serve for communication across the. Atlantic. 



The most recent improvements made toward perfecting this method 

 of transmission are those of Dr. Oliver Lodge, whose labors, continued 

 during the past few months, are still in progress. He has first 

 reorganized the transmitter apparatus so as to make it a more 

 persistent radiator. It emits longer trains of waves. This has been 

 accomplished by introducing in the path of the oscillations, between 

 the spark-gap and the wings, a few turns of stout wire to act as an 



