Mechanical Science applied to the Arts. 069 



6. Mr John Taylor stated, that by calculating from the duty 

 on steam-engines in Cornwall, it appeared, that work performed 

 by means of one bushel of coal, required ten or twelve years ago 

 two bushels; and in the time of Bolton and Watt's patent four 

 bushels were necessary : while, at the commencement of the use 

 of steam power, the coal required was sixteen bushels. The 

 steam engines at present in Cornwall were equal to 44,000 horse 

 power. 



7. Dr Lardner made some observations on rail-roads. He 

 stated that every road offers a sensible resistance to traction, but 

 this on a rail-road is less, because the surface is more uniform. 

 The resistance on a rail-road to the power of traction is always 

 the same, as the resistance produced by ascending an acclivity, 

 rising one foot in 250 ; that is, supposing the rail-road to be level. 

 Suppose a rail-road rising 1 foot in 250, resistance to traction 

 then proceeds from two causes, — the resistance on the level, as 

 already explained, and the resistance offered from the actual de- 

 clivity. The resistance to be overcome on the level is equiva- 

 lent to nine pounds per ton ; and on the road ascending 1 foot 

 in 250, it would be eighteen pounds per ton ; and thus it is seen 

 that, in the latter case, the drawing power must exert twice the 

 force necessary on the level. If the road rose 2 feet in 250, the 

 drawing force would be twenty-seven pounds to the ton. This 

 view of the subject is confined to ascents, but it should not 

 be forgotten, that when a rail-road is worked, the transit is from 

 one end to the other. It is necessary, in estimating the merits 

 of rail-roads, to consider their action downwards as well as up- 

 wards. In coming down a steep, no force is required to impel 

 an engine, and the gravity restores that force in going down 

 which it has robbed from it in the ascent. You have to provide 

 in an ascent of 1 foot in 250, for a resistance of eighteen pounds 

 to a ton, but in descending, no force is required. If it was 

 desired to strike an average between the ascent and descent, the 

 road would present a surface which would be equivalent to a 

 level. This point, respecting ascent and descent* struck the 

 House of Lords, before which he gave this opinion, as a para- 

 dox, but it was one only in sound and not in reality. Dr Lardner 

 remarked, that these observations referred to ascents not more 

 steep than 1 foot in 250 ; but supposing the rise to be 3 feet in 

 250, and where the stra : n would be, consequently, thirty-six 



