SECT, i.] THE STEAM ENGINE. 21 



ascending and descending strokes into the account; and in not considering the 

 moving power as a gravitating mass of matter. It is, therefore, more strictly 

 applicable to the question, though still not perfectly so, as the space, not the time, 

 should be given. (See Sect, iv.) 



22. The celebrated practical engineer", James Brindley, attempted to improve 

 the construction of the steam engine boiler by forming it of wood and stone, and 

 inserting a fire place and chimney of cast iron in the internal part of the boiler, so 

 as to surround both as far as possible, on all sides, by the water of the boiler. 

 This plan he expected would render more of the heat of the fuel effective ; and 

 therefore obtained a patent, in 1759, for the arrangement. That it was founded on 

 mistaken views of the nature of combustion, and of the quantity of the loss of heat, 

 would not be difficult to prove, (see art. 190.) ; and, accordingly, it never was 

 adopted in general practice. 



1762. Dr. JOSEPH BLACK ; born 1723, died 1799. 



23. The relation between the quantity of fuel and the effect of steam in an 

 engine became now an important subject ; but the different quantities of heat com- 

 bined with the same body according as it was in a solid, a liquid, or gaseous state, 

 or with different bodies at the same temperatures, had not yet been determined, or 

 rather the fact was not distinctly known ; and therefore crude opinion must have 

 directed the wisest, as it now directs the ignorant man, in his attempts to improve 

 the steam engine. To Dr. Black we owe the first investigation of the combination 

 of heat with bodies in the solid, liquid, and gaseous state, which he began to teach 

 publicly in 1762 : the heat so combining with them, he showed was insensible to 

 the thermometer, and hence he called it latent heat. 



The quantity of heat required to convert boiling hot water into steam, he found 

 exceeded five times the quantity which made water boil. Dr. Black also showed 

 that different bodies required different quantities of heat to produce the same 

 change of temperature, and denoted the property by the phrase, capacity for heat ; 

 the term now usually employed is specific heat. (See Sect. n. art. 70.) 



The principles of managing confined fires, and the nature and effect of fuel, 

 were also taught by Dr. Black. 



In the inquiries respecting heat he was followed by Dr. Irvine and Dr. Craw- 

 ford, who made experiments to determine the specific heat and latent heat of 

 various substances. 



1765. JOHN SMEATON, F.R.S. ; born 1724, died 1792. 



24. Smeaton was not of a cast of mind likely to seize the views of Dr. Black, 



