MECHANICS AND USEFUL ARTS. 61 



The American idea is cheap ens^ines. Their locomotives liave 

 their parts very accessible, ami they run them at fair l)ut not hio-h 

 speeds. The American engines have special arrangements tor 

 elearin^^ and lighting the road, and for burning wood in their 

 furnaces. Notwithstanding the superiority of English-made en- 

 gines, not one of them can run over American lines with any- 

 thing like the speed, safety, or endurance of their own. Strange 

 as this may at first appear, it is easily accounted for, and the exphi- 

 nation bears on the points we shall presently bring forward. The 

 explanation is, that the leading ends of tlie American engines are 

 supported on 4-wheeled truckvS, or bogies, which, while giving 

 a long wheel-base, and consequently steadiness, allow the engine 

 to travel on exceedingly bad roads, and to traverse sharp curves 

 with ease and security. 



The German engines go even slower than the French, Tlie 

 quickest French lines are those from Lyons to Paris, and from 

 Paris to Calais. The proportions of parts of all the foreign en- 

 gines — particularly the German — are very bad. For instance, 

 the cranks in many cases have double the quantity of material 

 necessary for the strength required, and this extra portion so dis- 

 posed as to be a perpetual stuml^ling-weight in their revolutions. 

 Of the Italian lines we know of nothing specific to be said. 



The Belgians run their engines at speeds intermediate between 

 the German and French; they follow a medium of English and 

 French make in their construction, and their lines contrast favora- 

 bly in their working with many others on the continent. This 

 may be attributed to their being under the general superintend- 

 ence of an Englishman. 



The Russians are much the same as the Germans. The engines 

 are mostly of English type, in some cases a cross between the 

 English and American. — London Herald. 



THE PRINCIPLE OF THE GIFFARD INJECTOR. 



Probably there is no mechanical device in common use which is 

 such a puzzle to mechanics and others as the Gifi:ard injector. Its 

 operation seems to defy the best-known laws of the equilibrium 

 of fluids, 5'et it acts effectualh', and under some circumstances is 

 preferable to the pump for feeding boilers with water. 



Its construction is simply a pipe fed from the steam space of the 

 boiler to the water space below the water level. The steam-lead- 

 ing pipe is contracted at its lower extremity, between the steam 

 and water level, in a space which is filled with the feed water, a 

 fine jet of steam acting against the feed water and forcing it into 

 the reception-pipe through a small aperture. Of course, neces- 

 sar}'' valves and cocks are emplo3"ed. 



A correspondent asks, what is the pirnciple employed in tlie 

 action of this injector? We cannot stat; it more clearly, so far 

 as it is understood, than to give the opinion of Mr. John Robin- 

 son, of Manchester, England. He says: "The pressure on all 

 parts of the interior of steam boilers being equal, some reason 

 6 



