on babbage's analytical machine. 99 



and the gear immediately connected with it. We have no means of 

 knowing, in the present state of the design, to what extent Mr. Babbage 

 had sncceeded in redncing this, or whether he had always been successful 

 in arranging his cams and cranks so as to secure the best working angles, 

 and to avoid their being jammed at dead points or otherwise. Giving 

 him full credit for being quite aware of the importance of this, we cannot 

 but doubt whether the design was ever in a sufficiently forward state to 

 enable him, or any one else, to speak with certainty on this point. Several 

 of the existing calculating machines show signs of weakness in the 

 driving-pinions. 



One of the movements apparently necessary to the tentative processes 

 of the engine is, when the spur-wheels on a given shaft have been brought 

 into certain definite positions depending on previous operations, to bring 

 up a sharp straight edge against them in a plane passing through the 

 axis of the shaft. This pushes some to right and others to left, according 

 to the position of the crown of the tooth relatively to the straight edge. 

 This operation is necessary to secure that the clearance of the different 

 parts of the machinery, whether originally provided in order to allow it 

 to work smoothly, or whether afterwards increased by working, shall not 

 introduce a numerical error into the result. The principle of this operation 

 is used generally throughout the analytical engine. Its consequent 

 effect, both in respect of the work which it throws upon the main driving 

 gear, and of the wear of the parts which it pushes, forms an important 

 element in considering the durability of the machine. This bar also 

 serves the purpose of locking part of the machine when required. 



On the other hand, it is to be remarked, that the use of springs has 

 been wholly discarded by Mr. Babbage, as directors of motion, although 

 he occasionally uses them for return motions. 



VII. Probable utilization of the Analytical Engine. 



It has been already remarked that one of the main features of the 

 engine is, that its function is coextensive with numerical synthesis and 

 solution, and that there is an absence of any special adaptation. In thus 

 widening the sphere of its capability, it is made to diverge from the 

 general tendency of mechanical design, which is towards the selection and 

 particularization of the work to be performed, and the restriction of the 

 machinery to one particular cycle of operation, usually within close 

 numerical limits, as well as limited in kind. Nevertheless, modern 

 engineering practice finds ample room for " universal " drills, shaping 

 tools, and other machines having very general adjustments and appli- 

 cations. But it remains practically true that each step of freedom of 

 adjustment is also a step in diminution of special aptitude. 



While the analytical engine is capable of turning out a single result, 

 as the combination of a complex series of numbers and operations per- 

 formed upon them, it can also yield a series of such results in a consecutive 

 form, and thus give tabulated results. Only it is not restricted, as is the 

 difference engine, to the special method of tabulation by finite differences, 

 nor is tabulation its primary function or intention. If its actual capa- 

 bilities are found to realize the intentions of its inventor, it will tabulate 

 all functions which are within the reach of numerical synthesis, and those 

 direct inversions of it which are known under- the name of solutions. It 

 deals, however, with number, and not with analytical form. 



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