NEW LIGHTS ON THE PROBLEM OF FLYING. 757 



tion. In fact, the art of managing a true flying macliine is so re- 

 fined and the skill required so great, and in the absence of such 

 skill the danger of a first attempt is so extreme, that probably 

 the only way to achieve true flight would be by the use first of a 

 dirigible balloon, and then gradually to decrease the sustaining 

 gas and substitute the aeroplane and propeller. 



In the distant future, and by means of such gradual ap- 

 proaches, the engineering difiiculties in the way of a true flying 

 machine may be finally overcome. If so, then we may look for 

 the greatest success in the direction of the work of Langley and 

 Maxim. 



Addendum, January 23, 1894-. 



The above article was finished and sent to the publisher some 

 time in October, 1893. In the January number of the American 

 Journal of Science Prof. Langley published an account of another 

 epoch-making series of experiments bearing on this subject. In 

 his previous series he showed the enormous importance of onward 

 movement in the sustaining power of an aeroplane. In this he 

 shows the enormous variation of velocity in air currents from 

 moment to moment. The whole air is in a violent turmoil from 

 varying currents. In the above article I have shown that soaring 

 and sailing are impossible without differential air currents ; but 

 the amount of difference of velocity of these currents shown by 

 Prof. Langley was wholly unexpected. These experiments, there- 

 fore, show that the supply of force from this source available to 

 the bird or to the flying machine is far greater than previously 

 supposed. While they do not seriously vitiate any of my conclu- 

 sions, they certainly place the subject of artificial flight in a still 

 more hopeful light. 



Mr. BRroE, of the Dundee antarctic whaling fleet, describes the whole of the 

 district south of 60 south latitude as strewn with icebergs, which become very 

 numerous south of 62. On one day the author counted at one time from deck 

 sixty-five of great size, besides many smaller ones. The highest berg seen from 

 his vessel, the Balaena, w^as about two hundred and fifty feet high; but many 

 were not more than seventy or eighty feet, the average possibly being about one 

 hundred and fifty feet high. All these bergs are tabular, or weather-worn varie- 

 ties of the tabular forms. They become pierced with caves, and these are some- 

 times connected with funnel holes, tJDrough which, as the swell beats up the 

 caves, immense columns of spray are projected. They may be finely castellated, 

 pillared, or arched. One was beautifully conical. The base of the bergs was col- 

 ored pale brown by marine organisms, and other brown streaks were seen be- 

 yond the water-level. No luminous glow was observed. "Clothed in mist, they 

 raise their mighty snow-clad shoulders to a stately height, or shine forth bril- 

 liantly in the sun. Although they are of the purest white, yet they glow with 

 color. The crevices exhibit rich cobaltic blue, and everywhere are splashes of 

 emerald gi-een." 



