Babbage's Economy of Machinerxj and Manufactures. 211 



tioned, I took the present reduced price of dolls' eyes 5 and calculating 

 that every child of this country not using a doll till two years old, and 

 throwing it aside at sexien, and having a new one annually, I satisfied 

 myself that the eyes alone would produce a circulation of a great many 

 thousand pounds. I mention this merely to show the importance of 

 trifles, and to assign one reason amongst many for my conviction that 

 nothing but personal communication can enable our manufactures to 

 be transplanted."' — pp. 199 — 201. 



Mr. Babbage mentions a very instructive example of the difficulty 

 of estimating the effects of a machine, and of the ingenious way in 

 which the difficulty was overcome. In order to fix a proper toll for 

 steam carriages, a Committee of the House of Commons endeavoured 

 to ascertain, from competent persons, the injury done by the atmo- 

 sphere to a well-constructed road, and then the proportional injury 

 which the same road sustained from horses' feet and from wheels. 



" Mr. Macneall," says Mr. Babbage, "as superintendent, under 

 Mr. Telford, of the Holyhead roads, proposed to estimate the relative 

 injury from the comparative quantities of iron worn oft" from the shoes 

 of the horses, and from the tire of the wheels. From the data he 

 possessed respecting the consumption of iron for the tire of the wheels 

 and for the shoes of the horses, of one of the Birmingham day coaches, 

 he estimated the wear and tear of roads arising from the feet of the 

 horses to be three times as great as that arising from the wheels. 

 Supposing repairs amounting to 100/. to be required on a road tra- 

 velled over by a fast coach at the rate of ten miles an hour, and the 

 same amount of injury to occur on another road used only by wag- 

 gons moving at the rate of three miles an hour, Mr. Macneall describes 

 the injury in the following proportions : 



One of the results of these experiments is, that every coach which 

 travels from London to Birmingham distributes about eleven pounds 

 of wrought iron along the line of road between these two places," — pp. 

 201—203. 



In treating of the effect of taxes upon manufactures, Mr. Babbage 

 has entered very briefly upon the subject of Patents, — a subject pe- 

 culiarly connected with that of his work, and to which he should have 

 allotted more space, and done greater justice. In the only paragraph 

 which relates to the present state of the law of patents, Mr. Babbage 

 remarks that 



" It is clearly of importance to preserve to each inventor the sole 

 use of his invention, until he shall have been amply repaid for the risk 

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