490 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1915. 



universally true, a large majority of the radical physical changes 

 have resulted from studies and developments made with a view to 

 extending the existing possibilities of telephony or telegraphy to 

 cover some new or more promising field. 



In selecting the items to be considered the endeavor has been to 

 touch upon those changes in the physical art of telephone and tele- 

 graph transmission which would be of interest to all of the members 

 of the Pan American Scientific Congress, irrespective of any com- 

 mercial, geographic, or climatic conditions which might be peculiar 

 to any given locality. In other words, the attempt has been to select 

 those developments which tend to improve or modify fundamental 

 considerations in the application of the art of transmitting intelli- 

 gence electrically. The only exception to this is in the brief discussion 

 of apparatus intended primarily for use under tropical and semi- 

 tropical conditions. To a large proportion of the members of the 

 congress this is really a fundamental consideration which must 

 underlie the proper engineering of the physical plant needed to give 

 service. 



Although the present state of the art has closely interlaced the 

 requirements of wire and radio telephone and telegraph develop- 

 ments and although the future seems to indicate an even closer tying 

 together of all phases of electrical intelligence transmission systems, 

 it is difficult in a short paper to treat the important advances, except 

 in relation with the particular field to which they most closely per- 

 tain. For this reason the discussion has been divided into three 

 main parts: 



1. Wire telephony, 



2. Wire telegraphy, and 



3. Radio communication, both telephonic and telegraphic. 



1. WIRE TELEPHONY. 



Since the whole present art of wire telephony is the result of only 

 40 years' work, almost anything might be construed as a " recent 

 development." Ten years has, however, been taken as the period to 

 be covered, and since any major development in the art requires 

 considerable time for its working out, the results of the work during 

 the past 10 years can only be properly appreciated by considering 

 the state of the telephone art some time prior thereto — for example, 

 about 1900. 



Let us review, therefore, the situation in the telephone field at the 

 beginning of the present century. 



By 1900 the telephone art was rapidly emerging from the era 

 when the inventor rather than the engineer was supreme in the field. 

 The experience gained during the preceding 25 years, supplemented 



