128 



SCIENCE. 



[Vol: II., No. 26. 



a locomotive is at work. Trials at Chicago 

 seemed to indicate that the engine was capa- 

 ble of maintaiiiiug steam with almost an_y kind 

 of fuel, and that the lignite and inferior coal 

 of the new north-west, which often contains 

 only thirt3--five per cent of carbon, can there- 

 fore be utilized under locomotives. 



The slow combustion does not produce a heat 

 intense enough to fuse the slag, and therefore 

 the firebars keep cleau and free from clinker ; 

 and it need hardlj' be pointed out that this is 

 an important practical consideration in deal- 

 ing with fuel which contains over fifty per cent 

 of ash. 



The large grate area is obtained l)y i^lacing 

 the fire and grate bars completely over the 

 driving-wheels, where plenty of width is ob- 

 tainable ; and the firebox is accordingly made 

 no less then 8 feet wide inside, instead of the 

 usual 33 inches. It might be anticipated that 

 the increased height of the centre of gravity 

 would tend to make the engine unsteady- at a 

 high speed ; but a precisely opposite result is 

 obtained, as the engine rides with remarkable 

 steadiness and smoothness, even at the highest 

 speeds. 



Thd Shaw engine has been so often de- 

 scribed, and been so promiuentlj- before the 

 public, that it is onl^' necessary to say here, 

 that, though exhibited at the Chicago exposi- 

 tion, want of time prevented anj- proper scien- 

 tific tests being made to ascertain the real value 

 of the invention. 





Metallic packing for piston-rods. 



Various forms of metallic packing for piston- 

 rods are now being extensively used with ex- 

 excellent results, the wear of both rod and 

 packing being very slight, while the use of anti- 



friction metal obviates the frequent renewals 

 necessary with hemp, rubber, and other pack- 

 ings which are destroyed by heat rather than 

 by wear. In the packing which we ilhistrate, 

 provision is made for any inaccuracy in fitting 

 by allowing the piston-rod some play in the 

 stuffing-box ; the vibrating cup, 4, sliding on 

 the ball and socket ring, 3. As the packing 

 rings are pressed to their work b3- a spring, it 

 is impossible for a careless engineer to screw 

 his packing too tight, or to make it bear on 

 one side onl3' of the rod. 



Wntcr. 

 Mack's improved lifting injector. 



The National tube- works of Boston, Mass., 

 exhibited an injector at work, which possessed 

 some points of noveltj', and appeared to be well 

 adapted for use on locomotives working with 

 bad water. The very fact that a simple ar- 

 rangement of hollow cones can enable steam 

 to lift and force water into a boiler working at 

 the same pressure is in itself a remarkable 

 paradox ; but Mack's injector, as shown at 

 worlv in the exposition, forced a small quantity 

 of water into a boiler working at two hundred 

 pounds per square inch when the injector itself 

 was only supplied with steam of half that press- 

 ure. The apparatus was so arranged that 

 the quantity of water forced against difterent 

 boiler-pressures bj' the same pressure of steam 

 could be readily gauged ; and the results were 

 interesting as showing what a large range of 

 work can be performed by an apparatus which 

 has no moving parts. The injector is made 

 in several pieces, so that it can be readily 

 taken apart, and cleaned of scale deposited b}' 

 hard or lime water. When the injector is 

 started, the water is lifted by means of a jet of 

 steam, which rushes through a very fine hole 

 running longitudinallj' through the centre spin- 

 dle ; the injector becomes full of water, which 

 escapes at the overflow ; the regulating spindle 

 is then screwed back, and the large volume 

 of steam thus admitted is condensed bj' the 

 water alreadj' in the injector, mingles with it, 

 and the momentum of the steam due to its 

 great velocit}- (some five thousand feet per 

 minute) drives the combined steam and water 

 into the boiler. 



