ARTIFICIAL FLIGHT. 537 



ment of Messrs. Renaud and Krebs of the French war de- 

 partment, who in 1885 constructed a war balloon called 

 " La France," capable of propulsion at a speed of about 

 fourteen miles an hour. Unfortunately, in order to stem 

 most of the winds that blow, a balloon would have to be 

 driven at some forty miles an hour, and herein lies the 

 the great difficulty which has prevented the /)/zis leger party 

 from making any great advances. Last year, however, 

 Dr. Wolfert's steerable balloon was shown in working order 

 at the Berlin Industrial Exhibition, and should have given 

 satisfactory results. The gas bag was of oval shape, nearly 

 100 feet long and 30 feet in diameter, and there were two 

 propellers, one about 9 feet in diameter in front of the 

 car acting horizontally, and another placed underneath to 

 raise and lower the machine. These propellers were to be 

 driven by an eight horse-power^ benzine engine making 

 500 revolutions per minute. Unfortunately, at a trial trip 

 on 1 2th June, the baloon exploded and burst into flames, and 

 both Dr. Wolfert and his assistant were killed. 



A new era was opened by the renaissance of the plus 

 ionrd ^'dviy which took place about the year 1891, with the 

 advent of an army of workers, including the names of 

 Maxim, Lilienthal, Langley, Pilcher, Chanute, Baden- 

 Powell, Phillips and others. All these are now familiar 

 names, and their apparatus and experiments have been so 

 widely figured and described by the Press that a mere 

 description of them here would hardly be of interest. To 

 understand their true significance, however, it is necessary 

 to consider one by one the various qualifications which are 

 required to make up a successful flying machine, and how 

 they have been attained. 



The problem of artificial flight will practically be solved 

 when a machine has been built which will raise itself and a 

 man off the ground into free air, which can be propelled 

 and guided for a certain distance in any desired direction, 

 even against a moderate wind, without fear of its breaking 

 or overturning, and which, with the experimenter, can be 



^ Aeronautical 'jfoiirnal, y an nary, 1891. 



