298 SOCIETY NAVAL ARCHITECTS AND MARINE ENGINEERS. 



number of persons on board are the same as in the American law. The American law, how- 

 ever, applies only to steam vessels, while the requirement of the convention applies also to 

 sail vessels or vessels propelled by other means than steam. Very few sail vessels have 

 crews of 50 or more. The convention requirements cover vessels propelled by the Diesel 

 engine or other forms of machinery not dependent on steam. 



Under the American law (June 24, 1910, Sec. 2) steamers plying between ports or 

 places less than 200 miles apart are exempt from the requirement to carry wireless apparatus. 

 The convention makes no such general exemption. If, however, it can be shown to the Gov- 

 ernment (Art. 32) that the route and conditions of a voyage render the requirement of 

 wireless apparatus unreasonable or unnecessary, vessels making such voyages may be ex- 

 empted if they do not go more than 150 miles from the nearest coast, or if within tropical 

 or semitropical waters (between the limits of 30° North latitude and 30° South latitude) 

 they take on temporarily native cargo-hands, or stevedores, thus for the time increasing to 

 over 50 the number of those on board. This custom obtains to a slight extent in the West 

 Indies, but more generally on the coasts of Africa and Asia. In the same waters where 

 native dhows or junks are used to an extent, a similar exemption on like conditions is per- 

 mitted. 



The only absolute exemptions from the requirement to carry the apparatus are in the 

 obviously necessary cases where a master at sea picks up shipwrecked persons or where he 

 is obliged to provide temporary substitutes for members of the crew who are ill or by di- 

 rection of Government is required to transport certain persons such as distressed seamen who 

 must be returned under the laws of most nations from foreign ports to their native land, 

 and by any of these methods the usual number cm board is increased above 50. 



Every ship equipped with wireless apparatus is also required (Art. 35) to carry an emer- 

 gency apparatus to be used in the event of the disabling of the ship's main dynamos on 

 which the power for the wireless apparatus in many cases depends. In substance, this re- 

 quirement is similar to the requirement of the American law for an auxiliary power supply. 

 The convention requirements, however, are more precise. The emergency apparatus must 

 be placed in its entirety in the upper part of the ship, as high as is practically possible in a po- 

 sition of the greatest possible safety to be determined by the Government, and must have an 

 independent source of energy which may be put rapidly into operation. The convention re- 

 quires that this apparatus must be capable of working for at least six hours. The Ameri- 

 can law requires a minimum of four hours. The convention requires a minimum range of 

 80 miles for larger vessels and 50 miles for smaller vessels. The American law requires a 

 minimum range of 100 miles for the auxiliary apparatus on all vessels. In this respect the 

 requirements of the convention are the same as those imposed by the London Radiotele- 

 graphic Convention of 1912 on a limited number of larger vessels. The present American 

 law is not in precise conformity with the Radiotelegraphic Convention. The differences, 

 however, are not essential, as the longer period of operation at the lesser range about equals 

 in efficiency the shorter period of operation at the longer range. As a practical matter the 

 range of radio apparatus cannot be precisely determined, atmospheric conditions, the sea- 

 son of the year, and other factors exerting more or less influence on range. Most apparatus 

 which covers 80 miles usually will also carry the signals to a distance of 100 miles or over. 



The advantages of having the wireless apparatus entirely independent of the ship's main 

 engines and dynamos connected therewith and of its installation on the highest part of the 

 ship with its own power supply directly under the control of the operators are obvious. 



