Mechanical Science applied to the Arts. 371 



forgotten, that they should have a regard to the power used. 

 If the power to be used was that of animals, then it might hap- 

 pen that the hilly road would be better than the level ; for no- 

 thing was better understood than that a dead and unvarying 

 pull upon the same set of muscles, would have the effect of caus- 

 ing the labour to be more severe, while a varying pull would 

 alternately give quiescence and exercise to the muscles. If the 

 line was so disposed as to throw the whole ascent in one pots, 

 the advantage would be gained of having the rest of the road 

 nearly level. But the cost of attaining this advantage should 

 not be forgotten. Steeps of this description required an in- 

 creased power, and the engines capable of working on the gene- 

 ral line of road would not be capable of exerting an increased 

 force. There were only two ways of ascendiog sudden ascents, 

 one by the agency of an additional engine, and the other by 

 having the whole train pulled up by means of a rope. The ad- 

 ditional engine would occasion much additional expense, for the 

 supply of them would always be preserved, and the men should 

 be paid their wages whether wanting or not. The use of the 

 rope w T ould occasion an enormous waste of power ; and he men- 

 tioned the instance of a place, where an ascent of 1 foot in 106 

 occurred. The rope was five miles long, and its weight was 

 60,000 pounds. Dr Lardner next referred to one point on 

 which he seemed to consider that engines generally were at va- 

 riance with what was correct. He contended, that the heat of 

 the fire is directly proportional to the quantity of the steam al- 

 lowed to escape in a definite time into the flue, and consequent- 

 ly that half the number of blasts of steam projected into the 

 chimney in an engine going up a hill, would have the same effect 

 in exciting the fire as double the number of blasts of half the 

 condensation, when the engine was running on a level plane. 



Friday, 8th August. — 8. Mr Ettrick read an account of certain 

 improvements on steam-engines, and on securing the steams of 

 boilers, of a machine for drilling boiler plates, and of an astro- 

 nomical clock. 



9. Mr Cheverton read a communication on the sculpture of 

 busts by machinery, exhibiting beautiful specimens. 



10. Mr Grubb made some very able and practical observa- 



