20 THE HISTORY OF [SECT. i. 



will enable us to do the most work with the least steam, and not the most work 

 in the least time with a cylinder of a given capacity ? (Sect, iv.) 



Mr. Blake also investigated the relation between the power and resistance which 

 gives a maximum effect in a given time when the motion accelerates from rest, 

 both when the force is uniform, and when variable, increasing as the distance. 1 

 (See Sect, iv.) 



1757. KEANE FITZGERALD, F.R.S. 



20. It was natural to expect that the atmospheric engine being now in con- 

 siderable use, the means of saving fuel would be considered, in places where it was 

 expensive. Mr. Keane Fitzgerald, in 1757, 2 proposed, with this object, to agitate 

 the water in the boiler by a stream of air, on Dr. Hales' plan for evaporating ; not 

 perceiving the difference between forming steam and accelerating evaporation. 

 But in consequence, Dr. Hales applied to him respecting working ventilators for 

 mines by steam engines ; and a rotary motion being necessary to that end, Fitz- 

 gerald contrived one to render the steam engine applicable to the purpose. The 

 method he adopted nearly resembled, in principle, that before contrived by Hulls for 

 his steam boat, (art. 14.) ; but instead of regulating it by a weight, Fitzgerald pro- 

 posed to use a fly wheel ; and remarks, that the steam engine by such means may 

 be applied to corn mills, raising coals, &c. Fitzgerald also showed the impropriety 

 of the then usual mode of constructing the working beam with its axis below its 

 centre of gravity, and altered the place of the axis of the engine beam of the York 

 water-works engine, with much advantage to its effect. 



1758. WILLIAM EMERSON ; born 1701, died 1782. 



21. A brief but clear description of the atmospheric engine was published by 

 Emerson in his ' Mechanics,' with the mode of computing its power, as far as 

 statical equilibrium between the power and resistance is concerned. He also, in 

 his ' Miscellanies,' gives a solution of a problem, which has for its object to deter- 

 mine the relation between the power and resistance when the effect is greatest. It 

 may be stated as follows : In a steam engine there is given the effective pressure 

 of the atmosphere upon the piston, and the length of the stroke, to find the water 

 to be drawn at a stroke, so that the greatest quantity shall be drawn in a given 

 time, supposing the force uniform, and the arms of the beam of equal length. 

 Emerson's solution differs from Blake's (art 19.), in taking the whole time of the 



- 



1 Phil. Trans, vol. li. p. i. or Abridg. vol. xi. p. 317. 



2 Phil. Trans, vol. 1. p. 53 and 157. 



