102 REPORT — 1878. 



to think that the cost of the engine, after the drawings are completed, 

 would be expressed in tens of thousands of pounds at least. 



10. We think there is even less possibility of forming an opinion as 

 to its strength and durability than as to its feasibility or cost. 



11. Having regard to all these considerations, we have come, not 

 without reluctance, to the conclusion, that we cannot advise the British 

 Association to take any steps, either by way of recommendation or other- 

 wise, to procure the construction of Mr. Babbage's Analytical Engine 

 and the printing tables by its means. 



12. We think it, however, a question for further consideration 

 whether some specialized modification of the engine might not be worth 

 construction, to serve as a simple multiplying machine, and another 

 modification of it arranged for the calculation of determinants, so as to 

 serve for the solution of simultaneous equations. This, however, inas- 

 much as it involves a departure from the general idea of the inventor, we 

 regard as lying outside the terms of reference, and therefore perhaps 

 rather for the consideration of Mr. Babbage's representatives than ours. 

 We accordingly confine ourselves to the mere mention of it by way of 

 suggestion. 



Third Report of the Committee, consisting of Dr. Joule, Professor 

 Sir W. Thomson, Professor Tait, Professor Balfour Stewart, and 

 Professor Maxwell, appointed for the purpose of determining 

 the Mechanical Equivalent of Heat. 



It will not be necessary to make a long report to the Association this 

 year. Dr. Joule has published a paper, giving in extetiso the experiments 

 summarized in the last two reports in the ' Philosophical Transactions of 

 the Boyal Society,' which was the medium of the publication of his former 

 paper in 1850. The new result, which confirms the old one, gives 772'55 

 foot-pounds as the equivalent at the sea level and the latitude of Green- 

 wich of the heat which can raise a pound of water, weighed in vacuo, 

 frcm 60° to 01° Fahr. of the mercurial thermometer, where the perma- 

 nent freezing point is called 32°, and the permanent boiling point of 

 water under a barometrical pressure of 30 inches of mercury raised to 

 G0° Fahr. is 212°. The work at present in hand is a more accurate 

 investigation of the true position of the freezing and boiling points of 

 the thermometers when cleared from the effects of the imperfect elasticity 

 of the glass of which they are constructed. The correction of the above 

 equivalent which may thus accrue is not expected to be of considerable 

 amount. 



