170 CHARLES BABBAGE. 



ference engine was intended to effect but one particular series of oper- 

 ations. It was not the general expression ev^en of one particular func- 

 tion, much less of any and all possible functions of all degrees of gen- 

 erality. Indeed, it could do nothing but add. It certainly performed 

 the processes of subtraction, multiplication, and division ; but then only 

 so far as these could be reduced to a series of additions. The analytical 

 machine, on the contrary, would have been able to add or subtract, mul- 

 tiply or divide — it could have done either and all with equal facility — 

 and it would have performed these operations directly in each case with- 

 out the aid of any of the other three. This fact implies everything. 

 The one engine merely tabulated but never developed; the other both 

 tabulated and developed. 



Mr. Babbage's third invention, which he named " difference engine, 

 No. 2," need not be dwelt upon here. It was never built. Its drawings 

 even were never quite completed. As an entity it had no existence out 

 of his own mind. In laboring to perfect the analytical machine he dis- 

 covered the means of simplifying and expediting the mechanical pro- 

 cesses of difference engine No. 1. The Earl of Eosse, who was greatly 

 interested in the application of mechanism to purposes of calculation, 

 and who was well acquainted with the drawings and notations of the 

 second difference engine so far as made, proposed that Mr. Babbage 

 should perfect and give them to the government, upon condition that 

 they would undertake to construct it. To this, with some reluc' ance, he 

 consented. It was then proposed to the Earl of Derby, he being prime 

 minister, that the government should apply to the president of the In- 

 stitution of Civil Engineers to ascertain — 



1st. Whether it was possible from Mr. Babbage's drawings and nota- 

 tions to make an estimate of the cost of constructing the machine. 



2d. In case this question was answered in the affirmative, then could 

 a mechanical engineer be found who would undertake to construct it, 

 and at what expense. 



It was explained to Lord Derby that the cessation of work upon the 

 first difference engine was owing to no fault of Mr. Babbage; that, being- 

 new in design and construction, and requiring the utmost mechanical 

 skill for its execution, it had necessarily been costly ; that the necessitj- 

 of constructing and, in many instances, inventing tools and machinery of 

 great complexity for forming with requisite precision parts of the appa- 

 ratus dissimilar to any used in ordinary mechanical works, had produced 

 unavoidable delays, and that the foremost men of practical science all 

 over Europe who were acquainted with the facts, so far from being sur- 

 prised at the time and expense that had been required to bring the 

 engine to its then present state, felt much more disposed to wonder that 

 it had been possible to accomplish so much. " If this work," Mr. Bab- 

 bage wrote to the minister, "upon which I have bestoAved so much time 

 and thought were a mere triumph over mechanical difficulties, or simply 

 curious, or if the execution of such engines were of doubtful practica- 



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