246 APPLIED SCIENCE 



should be known without proof, that there is a real difference 

 between ignorance and knowledge, between care and neglect ; 

 and that supervision after submersion is not less necessary than 

 during manufacture. The main object of this article has been 

 to show that the success obtained in late years, as compared 

 with early failures, is due to no chance, but to a real advance 

 in every branch of Submarine Telegraphy. If the reader does 

 not understand or believe in this advance, the writer has failed 

 in his object. He prefers to think that he has shown good 

 reason for believing that the success is likely to be permanent. 

 Much might be written on the proposals for still further 

 improvements, real and imaginary. Mr. Hooper has succeeded 

 in preparing india-rubber, so as to be apparently permanent, 

 while it certainly surpasses gutta-percha in all the electrical 

 properties which are required for the insulation of cables. 

 The Indian Government has taken the initiative in employing 

 this material, which is eminently suited for tropical climates. 

 The other preparations of india-rubber have very generally 

 been found subject to decay ; and various newly proposed ma- 

 terials, such as parkesine and balata, can hardly be said to have 

 been fairly brought before the public. 



Messrs. Siemens have employed for some portion of their 

 lines lately laid with success in the Mediterranean a very novel 

 form of cable, formed of hemp bound with strips of copper, 

 which they believe will be much more permanent than the old- 

 fashioned cables. The forms proposed, but not yet tested, are 

 very numerous, and little is known of their merits. The cost 

 of an experiment is so great that engineers hesitate to recom- 

 mend even what they believe to be well worth a trial. It is 

 certain that the old forms answer well, but it is equally 

 certain that their expense will preclude their adoption, except 

 on the main lines. A cheap light cable, durable in deep water, 

 would lead to an immense extension of the telegraphic system. 

 It is by no means certain that a simple gutta-percha-covered 

 wire would not answer as well as the most elaborate cable. 

 However this may be, the next advance must be towards 

 cheapness ; efficiency is attained. 



The importance of telegraphic communication is often 

 claimed on very narrow grounds. The advantages in war and 



