NO. 3 LANGLEY MEMOIB ON MECHANICAL PLIGHT 125 



I assume thai no public statement will be made by the permission of the 

 Board until the work is terminated, but thai I may publish ultimately at my 

 discretion a statement of any scientific work done in this connection. 



I understand thai the exercise of this discretion includes the ordering and 

 purchase of all material by contract or in open market, and (lie employment of 

 any necessary help, without restriction, and that, while I desire that no money 

 shall pass through my hands, itemized bills for each expenditure, made in proper 

 form and approved by me, will be paid by the Chief Signal Officer. 



Much has already been spent at the Smithsonian Institution for the pur- 

 pose in question, in special apparatus, tools and experiments, and in recent 

 constructions now actually going on, which have involved still more time than 

 money, and which are essential for experimental use in building the proposed 

 machine; and since to re-create all this independently would greatly defer prog- 

 ress, I assume that my discretion includes the decision as to how far this shall 

 be used and paid for at the cost of this allotment (it being understood that I 

 have no personal property in any of the material which might be transferred for 

 the purpose of the work) ; and I also assume that my discretion includes the de- 

 cision as to where the work shall be conducted — that is, whether in shops al- 

 ready constructed, or in others to be elsewhere erected or rented, with the nec- 

 essary adjuncts, whether on land or water, and generally whatever is necessary 

 to the earliest attainment of the object desired by the Board. 



S. P. Langley. 

 Smithsonian Institution, Washington, D. C, 



December 12, 1898. 



As is always the case in experimental work, especially in a field so very new 

 as was the field of aerodromics at the time that this larger construction was un- 

 dertaken, the " plant," or shops and laboratories required for the constructional 

 and testing work, grew to a size far beyond what seemed even remotely pos- 

 sible at the beginning of the work; and even the mere administration involved in 

 the carrying on of this work proved to be no inconsiderable matter before it had 

 progressed very far. 



The years of experiment with the models had demonstrated clearly that the 

 greatest difficulty in the development of the aerodrome was the construction of 

 a suitable power generator, which should combine the elements of extreme light- 

 ness and unusual power with a fair degree of durability. Although remarkably 

 good results had been secured in the case of the models through the use of steam, 

 it was realized from the first that not only would the development of a steam- 

 power plant for a large man-carrying aerodrome present difficulties of a con- 

 structional nature, but that such a steam plant would necessarily be so fragile 

 and delicate as to make it a constant menace to the machine which it was to pro- 

 pel. The solution of the difficulty, it was believed, was to be found in the use of 

 an internal combustion engine; but Mr. Langley had had very little experience 

 with such engines, and was averse therefore to undertaking the construction of 

 a large aerodrome until he had assurance that a suitable gasoline engine could 

 be secured. Before making an agreement to attempt the work for the War De- 



