322 



SCIENCE. 



[Vol. XII. No. 



tightly closed, having neither grate-bars nor ash-pit. Into the front of 

 this chamber, and on the same level, there enter two short horizontal 

 pipes, or tuyeres, about two feet apart. The outer ends of these tuyeres 

 are connected to a main air blast-pipe, which is kept filled with air 

 under a slight pressure by means of an ordinary blower. Simple 

 valves permit the ready and accurate adjustment of the amount of 

 air passing through the tuyeres into the combustion-chamber. Be- 

 tween and slightly above these tuyeres is a small rectangular hop- 

 per, into the top of which the finely pulverized coal is fed by screw- 

 conveyers. The coal is fed out of the hopper by means of an 

 ordinary screw of about two inches diameter, which passes hori- 

 zontally through the lower portion of the hopper, issuing from its 

 opposite sides through holes just large enough to loosely fit the 

 outside of the screw. The pulverized coal lodges between the 

 threads of the screw, and, on revolving the latter, the coal is fed out 

 through the side of the hopper. One end of the screw is right- 

 handed, and the other is left-handed, though both ends are of the 

 sdme pitch. It follows, therefore, that the coal will be fed out of 

 both ends of the hopper at exactly the same rate, this rate depend- 

 ing on the speed of revolution of the screw. The coal is kept from 

 packing or becoming solidly wedged in the hopper by means of an 

 agitator kept in motion immediately above the feeding-screw. On 

 issuing from the hopper, the pulverized coal drops into the tuyeres 

 directly below, and is carried to the combustion-chamber by the 

 blast of air passing through the tuyeres, becoming intimately mixed 

 with this air at the same time. Only enough air is admitted to se- 

 cure complete combustion, thus avoiding the great loss due to the 

 excessive amount of air necessarily admitted when burning lump- 

 coal on an ordinary grate. The feeding-screw is operated by gear- 

 ing driven from a convenient line of shafting, such arrangements 

 being made as will secure a readily and accurately adjustable mo- 

 tion of the screw, and hence a readily and accurately adjustable 

 feed of the fuel. 



As the relative as well as absolute amounts of coal and of air can 

 thus be adjusted at will, and with any desired degree of precision, 

 it follows that the character and intensity of the flame are com- 

 pletely under control. The ability to thus produce, and maintain 

 for any desired length of time, a flame of any desired intensity, and 

 either reducing, neutral, or oxidizing in character, carries with it, 

 for metallurgical purposes, many advantages too well known to 

 need more than a passing allusion. 



In the Chester Rolling Mills the apparatus was attached directly 

 to the combustion-chamber of one of their regular puddling-fur- 

 naces, though greater economy would probably have been obtained 

 by the use of a special form of combustion-chamber devised for 

 this purpose. The coal was the same as that used for all the other 

 puddling-furnaces, except that it was pulverized. No conveyers were 

 fitted to feed coal into the hopper, the coal being furnished in bags 

 of one hundred pounds each, which were emptied into the hopper 

 as required. As thus applied, this process realized a very large 

 measure of success. The furnace was heated more rapidly after 

 charging than the other furnaces, which were being worked in the 

 ordinary manner, though with the same iron. More heats were 

 obtained per day with the new process, less fuel was consumed 

 per ton of iron produced, less iron was wasted in puddling, and 

 the iron produced proved to be of slightly superior quality. 

 There was no smoke, and the ashes was carried out of the top of 

 the chimney in the form of fine dust, invisible from the ground. 

 While charging the furnace, the supply of both air and fuel was 

 completely stopped, thus preventing waste, and enabling the men 

 to work more quickly. In considering the superior economy of this 

 process, it must be borne in mind that the actual economy in the 

 production of heat from any given fuel does not represent the total 

 gain ; for by this process very cheap and otherwise comparatively 

 useless slack coal and coal-dust will answer nearly all purposes, 

 thus presenting another material advantage. 



It is of course impossible to give exact figures, except from ob- 

 servations extending over a much longer period of time than was at- 

 my disposal at Chester. There can, however, be no question that 

 the McAuley process effects a considerable and substantial gain in 

 economy of fuel-consumption. There remains simply the determi- 

 nation of the exact amount of this gain by means of accurately 

 conducted experiments by scientific and practical experts. 



The process has very recently been applied to the puddling-fur- 

 naces of the Warren Iron and Steel Company at Warren, O., and 

 the success obtained seems to have been very great. A report of 

 the trial there given this process has just reached me, and reads as 

 follows : — 



" The results of the trial just completed at the works of the 

 Warren Iron and Steel Company, Warren, O., with the McAuley 

 pulverized fuel system, are remarkable. The trials covered forty- 

 six on two of the puddling-furnaces. The furnaces were charged 

 with 23,000 pounds of iron during the trial. The amount of pul- 

 verized coal used was 12,260 pounds (a little over six tons). The 

 cost of this fuel was $5.43. The amount of iron drawn from the 

 furnaces was 24,029 pounds, an excess of 1,029 pounds over the 

 amount put in the furnaces originally. This is what the McAuley 

 system accomplished. 



" By the old process, now in use, during the same heats, the 

 amount of coal required was 36,920 pounds (over eighteen tons), the- 

 cost of which was $16.50 : in other words, the McAuley process 

 saved nearly 75 per cent of fuel. The McAuley process increased 

 the amount of iron 5*^ per cent ; that is, there was 5-J^ per cent more 

 iron taken out by the new process than was charged. This gain is 

 worth $15.45 : in other words, the gain in iron alone pays for 

 nearly three times as much coal as is required by the McAuley 

 process. The iron-men who witnessed the trials were astonished' 

 at the remarkable results. The iron gained by the McAuley pro- 

 cess comes from the ' fix ' which is used to protect the pan and sides 

 from the intense heat, and also from the cinder, containing 50 per 

 cent of iron, which is put in the furnaces to flux the iron. By the 

 old process this is all lost, and in addition there is generally over 5. 

 percent of waste. This means practically an actual gain of 10 per 

 cent of iron by the new system." 



The puddling process makes specially severe demands on any- 

 such automatic fuel-feeder ; and hence even better results may be 

 expected from the application of the new process to steam-boilers, 

 both land and marine. It should prove especially valuable in ma- 

 rine 'boilers ; for not only would the required speed be developed at 

 less expense, but less coal would have to be carried for any givea 

 trip, and the space and weight so gained would, of course, be avail- 

 able for carrying paying freight. 



Without going into any further details, it may be broadly stated 

 that there are very few cases in which fuel is consumed in large 

 quantities, where it could not be burned more advantageously in 

 the pulverized form ; and, as there can be no question that the Mc- 

 Auley economizer is the best apparatus yet invented for this pur- 

 pose, it seems as though it were destined to work a great revolution 

 in the manner and economy of consumption of fuel. 



In conclusion, it may be of interest to state that the coal is pul- 

 verized for this process by means of the Cyclone pulverizer, the 

 principle of which is fairly indicated by its name. Within a closed 

 chamber a pair of wheels resembling three-bladed screw-propellers 

 revolve very near each other at a great velocity, but in opposite 

 directions. Two powerful currents of air in opposite direc- 

 tions are thus generated, their joint effect being to produce a min- 

 iature whirlwind within the chamber. Into the vortex of this en- 

 closed cyclone the coal is regularly dropped, and is rapidly ground 

 into the finest powder by the mutual attrition of its particles. 

 There is no grinding or pulverizing by the direct action of any of 

 the metal parts of the machine, so that the machine does a great 

 deal of work with extremely little wear. X. 



PROFILES OF THE NICARAGUA AND PANAMA 

 CANALS. 



The failure of the Panama Canal Company makes the uninter- 

 rupted continuance of work on the canal very doubtful, and thus 

 the chances of the Nicaragua Canal being the first to be completed 

 have materially increased. The profiles on p. 323 show a compar- 

 ative statement of the amount of excavating to be done in both 

 canals ; and it will be seen at a single glance, that, even con- 

 sidering the amount of work already accomplished at Panama, the 

 Nicaragua route is by far the less difficult. The profiles do not 

 show the works necessary for protecting the canal, such as dams. 



