22Q Notices respecting New Books. 



correction of the constants. — The mechanical power of compressed 

 gases is examined ; and it is inferred,that the steam of water possesses 

 greater advantages for use in an engine, than the vapour of any other 

 liquid. — Rules are next given to find the volume the steam of a 

 given quantity of water occupies at a given force and temperature ; 

 the laws of the mixture of steam and air, as in the air-pump of an 

 engine; and the laws of the motion of steam in the passages, &c. of 

 engines, with the loss by cooling ; and a curious inquiry respecting 

 the temperature of condensation which affords the maximum of 

 useful effect in the old atmospheric engines ; illustrated by a re- 

 ference to Mr. Watt's experiments, with a model of one. The sec- 

 tion concludes with the investigation of the formula for the escape 

 of steam at safety-valves. 



The third section is on the generation and condensation of steam, 

 and the apparatus required j first treating of combustion and com- 

 bustibles, with an extensive table to show the relation between the 

 heat afforded by bodies, and that which their constituent elements 

 would give : then the conditions favourable to the process of com- 

 bustion are considered, and the quantity of the gaseous products, 

 with rules for the supply of air, and size of chimneys. The relation 

 between the surface of boiler to be exposed to heat, and the quan- 

 tity of steam to be generated ; and of the capacity of the boiler to 

 the effective power of the engine, are also exhibited, and compared 

 with practice ; and then rules given to fulfil the essential conditions. 

 The different species of boilers, fire-places, safety-valves, and other 

 apparatus, are then described ; and the section closes with the prin- 

 ciples of condensation, the quantity of water required to produce 

 it, and a tabular view of the methods that may be used, referring 

 to the dates of the first use of them in the steam-engine. 



The fourth section commences with a popular illustration of the 

 nature and modes of obtaining- the power of steam, and their relative 

 advantages 5 next, proceeding to show how to calculate the utmost 

 effect steam can possibly afford to produce rectilinear motion ; and 

 afterwards its effect in rotary engines, — showing the loss of effect in 

 the latter to be constant, and in some cases very considerable. The 

 modes of applying the power of steam are classified, with their com- 

 binations ; and then the laws which determine the relations of the 

 parts for cylinder engines, so as to afford a maximum of useful effect 

 with a given quantity of steam ; the capacity of the air-pump, and 

 the power lost in working it. 



The fifth section treats of the proportions, power and constructions 

 of noncondensing engines, usually called high-pressure engines, 

 showing the causes of loss of power, and the means of estimating the 

 quantity of loss ; the best proportion for cutting off the stroke when 

 the steam acts expansively -, and the theory of combined cylinder ex- 

 pansive engines. 



The sixth section treats of condensing engines. After a general 

 view of their nature, and a classification of the methods of construc- 

 tion, the proportions, causes of "loss, and the power of the atmo- 

 spheric engine are investigated j and also in its combination with a 



separate 



