656 



Popular Science Monthly 



inboard by mechanical exhausters and in 

 turn pumped overboard. Underneath 

 the hull the exhaust is sprayed out and 

 carried back to the propellers. If there 

 are any bubbles left they are churned up 

 by the propellers as by an egg-beater. 

 Thus the betraying wake left by a train 

 of air bubbles is to be eliminated. 



The noise from oil engines under 

 water, to which objection has been raised 

 by naval ofhcers, is caused by a final ex- 

 pansion of gas, after it leaves the cylin- 

 ders, from a pressure of about fifty 

 pounds down to atmospheric. This is 



one can say. The Nav>' is frankly inter- 

 ested in the project, but, following the 

 usual government policy, it prefers to 

 adopt the system only after it has been 

 completely developed by some private 

 company. About $300,000 have been 

 thus far spent on the system. Its 

 promoters are unwilling to make any 

 further sacrifices. Here we have a good 

 example of the use of a Naval Advisory 

 Board. The Neff system may not be 

 perfect ; but it has assuredly commenda- 

 ble features enough to justify the Board 

 in carrying on the further development 



The llama of South America corresponds to the camel of the East as a beast of burden 

 in the desert regions of the Andes 



accompanied by rapid sharp reports and 

 a reverberating roar. In the Neff system 

 it is claimed that the exhaust is silent, 

 because the engine is exhausted into a 

 condenser or a closed chamber from 

 which it is drawn at a partial vacuum and 

 discharged overboard at nearly the out- 

 side water pressure. The remaining 

 noises are due to the movements of the 

 machine parts, such as the clicking of 

 valves. AH this noise, it is claimed, may 

 be reduced by proper regulation and ad- 

 justment. In testifying before the Com- 

 mittee on Naval Affairs of the House of 

 Representatives, Mr. Neff pointed out 

 what the Popular Scienxe Monthly 

 has already shown — tliat the characteris- 

 tic hum of an electric motor can be picked 

 up at a distance of fifteen miles by micro- 

 phones and that this hum is easily dis- 

 tinguished from the vibration of engines. 

 Hence there is just as much objection to 

 the electric motor as to the Diesel engine 

 under water. 



Whether or not the Neff system will be 

 adopted by the United States Na\y no 



with government funds. If private com- 

 panies were to wait for inventors to sub- 

 mit commercially perfect devices we 

 would have no tungsten lamp, no 

 harvesting machinery, no electric motor. 

 All new inventions are crude. They 

 must be regarded as material for de- 

 velopment by laboratory' engineers. Not 

 until the government assumes that at- 

 titude are we likely to improve our 

 fighting machinery. 



Llamas as Powder- Carriers 



IN the semi-desert Andes countries the 

 llama is the general beast of burden, cor- 

 responding to the camel in the Old 

 World. The photograph shows a troop 

 of these singular animals transporting 

 American powder to an interior Bolivian 

 mining district, far from any railroad. 

 The llamas are heading for the Andean 

 Mountain passes, led by a reliable old 

 bellwether. Two or three gauchos 

 (herdsmen) will manage a bunch of fifty 

 or sixty animals; for the creatures give 

 little or no trouble unless overloaded. 



