4 EXPERIMENTS IN AERODYNAMICS. 



I have now been engaged since the beginning of the year lss7 in experiments 

 on an extended scale for determining the possibility of, and the conditions for, 

 transporting in the air a body whose specific gravity is greater than that of the 

 air, and I desire to repeat my conviction that the obstacles in its way are not 

 such as have been thought; that they lie more in such apparently secondary 

 difficulties as those of guiding the body so that it may move in the direction 

 desired, and ascend or descend with safety, than in what may appear to be the 

 primary difficulties due to the nature of the air itself, and that in my opinion 

 the evidence for this is now sufficiently complete to engage the serious attention 

 of engineers to the practical solution of these secondary difficulties, and to the 

 development of an art of mechanical flight which will bring with it a change in 

 many of the conditions of individual and national existence whose importance can 

 hardly be estimated. 



The way to this has not been pointed out by established treatises on aero- 

 dynamics, whose fundamental postulates, like those of any other established 

 science, may be held to contain implicitly all truths deducible from them, but 

 which are so far from being of practical help here, that from these postulates 

 previous writers of the highest repute have deduced the directly opposite con- 

 clusion, that mechanical flight is practically impossible. * Reason unaided by 

 new experiment, then, has done little or nothing in favor of the view now taken. 



It may be asked whether it is not otherwise with statements which are 

 authorized by such names as that of Newton, and whether a knowledge of truths 

 mathematically deducible from them, would not at any rate furnish a test to 

 distinguish the probably true from the probably false; but here it is important 

 to remember that the mathematical method as applied to physics, must always 

 be trustworthy or untrustworthy, according to the trustworthiness of the data 

 which are employed; that the most complete presentation of symbols and pro- 

 cesses will only serve to enlarge the consequence of error hidden in the original 

 premises, if such there be, and that here, as will be shown, the error as to fact 

 begins with the great name of Newton himself. 



In this untrodden field of research, which looks to mechanical flight, not by 



means of ball is, but by bodies specifically heavier than the air in which they 



move, I think it safe to say that we are still, at the time this is written, in a 

 relatively less advanced condition than the study of steam was before the time 

 of Newcoraen ; and if we remember that such statements as have been com- 

 monly made with reference to this, till lately are, with rare exceptions, the product 

 of conjecture rather than of study and experiment, we may better see that there 

 is here as yet, no rule to distinguish the probably important from the probably 

 unimportant, such as we command in publications devoted to the progress of 

 already established sciences. 



See paper by Guy-Lussac and Navier, cited later. 



