Tredgold on the Steam- Engine. 221 



separate condenser. The steam-pressure engines of Boulton and 

 Watt, both single and double, is next considered, with the construc- 

 tion of them either for expansive action, or not, and all the causes of 

 loss of power, and the proportions of the parts in detail j also the 

 combined engines of Hornblower and Woolf are treated of in a simi- 

 lar manner. 



The seventh section is occupied by the construction of the parts 

 common to most engines j as valves, slides, pistons ; with the mode 

 of estimating their friction, methods of moving valves, &c. cranks, 

 parallel motion apparatus, and practical rules for the strength of the 

 parts of engines, with the conditions necessary for safety in boilers, 

 and the mode of estimating the effect of irregular expansion on the 

 strength of boilers of cast-iron, — closing with the methods of joining 

 the parts of engines together. 



The eighth section is on equalizing the action, regulating the 

 power to the effect, measuring the quantity of useful effect, and ma- 

 naging the working of engines j describing, with investigation when 

 required, the fly and counterweight to equalize the action, the throttle 

 valve, Field's valve, #ie conical pendulum, the regulator and the ca- 

 taract to regulate the power j and the gauges, indicator, and counter, 

 to show the state of the parts, and how by friction the useful effect 

 of any engine may be measured at a trifling expense j and lastly, 

 the circumstances to be chiefly attended to in working the engine. 



The ninth section is on the application of the steam-engine to va- 

 rious purposes -, first, generally to raising water, then its particular 

 cases, as the drainage of mines, the supply of towns, with a table of 

 the supply to towns in ancient and modern times ; secondly, to im- 

 pelling machinery for manufacturing purposes j thirdly, its applica- 

 tion to agricultural purposes 5 and lastly, its application to steam car- 

 riages. 



The tenth section is on steam navigation, treating of the longitu- 

 dinal and lateral stability of vessels, and the resistance of vessels ; in 

 the latter inquiry a new theoiy of resistance is adopted, which ap- 

 pears to give results nearly according with practice. The various 

 modes of propelling vessels are noticed, and those by water-screws 

 and paddle-wheels are investigated, and the modifications pointed 

 out ; then the strength of vessels, the power of sails and of currents, 

 and their combination with steam power, followed by the necessaiy 

 rules for arranging the proportions, power, and effect of vessels, and 

 a tabular view of the vessels, executed at different times by the best 

 manufacturers in this country. 



These multifarious inquiries are followed by an extensive table of 

 the properties of steam, and two tables of the proportions of engines 

 for different powers, with the expenditure of water and fuel each re- 

 quires. The letter-press is illustrated by wood-cuts in the pages, and 

 the whole by twenty plates, each having its description opposite to 

 it; and a copious index, and a full table of contents, renders reference 

 to particulars easy ; and, as a whole, this most useful work presents 

 that combination of science with practice, which perhaps no one, ex- 

 cept a person having the experience of a workman, as well as an 



extensive 



