98 bepoet— 1878. 



every particular movement essential to the design of the engine ; but, for 

 the most part, they are not working drawings, that is to say, they are not 

 drawings suited to be sent straight to the pattern or fitting shop, to be 

 rendered in metal. There are also drawings for the erection of the 

 ■engine, and there appears to be a complete set of descriptive notes of it in 

 Mr. Babbage's "mechanical notation." There remains, however, a great 

 deal to be done in the way of calculating quantities and proportions, and 

 in tbe preparation of working drawings, before any work could actually 

 be set in hand, even if the design be really complete. There is some doubt 

 on this point as the matter stands, and it certainly would be unsafe to rely 

 upon the design being really complete, until the working drawings had been 

 got out. Mechanical engineers are well aware that no complex design 

 can be trusted without this test, at least. 



It was Mr. Babbage's rule, in designing mechanism, in the first place 

 to work to his object, in utter disregard of any questions of complexity. 

 This is a good rule in all devising of methods, whether analytical, 

 mechanical, or administrative. But it leaves in doubt, until the design 

 finally leaves the inventor's hands in a finished state, whether it really 

 represents what is meant to be rendered in metal, or whether it is simply 

 a provisional solution, to be afterwards simplified. 



V. Provable Cost. 



It has not been possible for us to form any exact conclusion as to the 

 • cost. Nevertheless there are some data in existence which appear to fix 

 a lower limit to the cost. Mr. Babbage, in his published papers, talks of 

 having 1,000 columns of wheels, each containing 50 distinct wheels ; this 

 apparently refers to his store. Besides the many thousand moulded 

 pewter wheels for these, and the axes on which they are mounted, there 

 is the mill, also consisting of a series of columns of wheels and of a vast 

 machinery of cams, clutches, and cranks for their control and connection, 

 ■so as to bring them within the directing power of the Jacqnard systems 

 of variable cards and operation cards. Without attempting any exact 

 estimate, we may say that it would surprise us very much if it were found 

 possible to obtain tenders for less than 10,000L, while it would pretty 

 certainly cost a considerable sum to put the design in a fit state for 

 obtaining tenders. On the other hand, it would not surprise us if the cost 

 were to reach three or four times the amount above suggested. 



It is understood that towards the close of his life Mr. Babbage had 

 contemplated carrying out the manufacture of the engine on a smaller 

 scale, confining himself to 25 figures instead of 50, and to 200 columns 

 instead of 1000 or more. This would of course reduce the amount of 

 the metal- work proportionately, but we do not think that it would mate- 

 rially reduce the charge which we anticipate for bringing the design into 

 working order. 



VI. Strength and Durability. 



The questions of strength and durability had by no means escaped Mr. 

 Babbage's attention, and a great deal of his detail bears marks of having 

 been designed with especial reference to these two points That was 

 essential in a large amd complex engine with some thousands of whe els, all 

 requiring at some time or other, although not simultaneously, to be driven 

 by the means of one shaft. This necessarily throws a great deal ot 

 pressure, and also a grv«*t deal of wear and tear, on the mam driving shatt 



