VI NOTES BY THE EDITOR. 



and form peaceable, progressive, and permanent communities, 

 in striking contrast with the disorderly, miscellaneous, and fugi- 

 tive crowds rushing to localities of gold and silver discoveries. 



From George Stephenson's locomotive, in 1824, which travelled 

 at the rate of six miles an hour, to that of 1867, which has reached 

 a speed of seventy miles an hour, what a wonderful advance ! This, 

 in fact, is the emblem of the present era, abridging labor, facili- 

 tating commerce, and by rapid locomotion entirely changing the 

 character and conditions of society. 



Steel is now extensively used for locomotive boilers, fire-boxes 

 and tubes, tires, piston-rods, and motion-bars, and for bridge 

 construction. The age of iron is gradually passing away, and the 

 age of steel is taking its place, the latter material being stronger 

 and lighter. 



According to Prof. Rankine, it is a law of thermodynamics that 

 the utmost quantity of work that can be got by the expenditure 

 of a given quantity of heat depends solely on the limits of tem- 

 perature between which the engine works, and is independent of 

 the nature of the fluid to which the heat is applied, such as water, 

 ether, air, etc. The means of increasing the economy of heat in 

 thermodynamic engines are of three kinds : 1. Working expan- 

 sively, so as to obtain from the heat applied to the fluid all the 

 work possible between given limits of temperature ; this has prob- 

 ably been carried to the utmost extent practicable. 2. Increasing 

 the range between the limits of temperature, to which bounds are 

 set in practice by the conditions of durability and safety. 3. 

 Diminishing the amount of heat wasted in the furnace by imper- 

 fect combustion, etc. It is in the last direction that the greatest 

 improvements are now to be looked for ; cast-iron boilers in sec- 

 tions with free circulation of water in thin films, the introduc- 

 tion of the air necessary for perfect combustion and the prevention 

 of smoke, and the use of petroleum and other concentrated fuels, 

 are now the points to which the attention of practical engineers 

 is directed. 



English agricultural journals speak highly of steam cultivation, 

 though from inexperience, want of confidence, and want of capi- 

 tal, it makes slow progress. Its evident advantages, its economy, 

 and the simplicity and perfection of the machinery and imple- 

 ments, must soon obtain for it a general adoption. 



A great revolution in metallurgical processes is promised by 

 the use of pulverized fuel, utilizing all the heat of combustion at 

 the time and place where it is wanted, and bringing into profitable 



