1S41.J 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



65 



preferred by blacksmiths for their forge on account of its caloritic strength 

 and freedom from sulphur, give off in iguition 32-5 parts, and leave 67-5 of a 

 bulky, compact coke. 



Every coal which contains much hydrogen, and, therefore, loses much 

 weight by ignition in retorts, necessarily produces nmch smoke, with a great 

 waste of heat in our common steam boiler furnaces, for reasons which you 

 have so well developed in your treatise. "MTien a carhuretteil hydrogen," 

 says Liehig, " is kindled, and just as much oxygen admitted to it as will con- 

 sume its hydrogen, the carbon does not burn at all, hut is deposited (or 

 separated) in (he form of soot ; if the quantity of oxygen is not sufficient to 

 burn even all the hydrogen, carburets of hydrogen are produced poorer in 

 hydrogen than the" original carburetted hydrogen."t The above gas and 

 smithy coals which, from their richness in hydrogen, are capable of afTording 

 the greatest proportion of heat by thorough combustion, afford often a much 

 smaller quantity than the Llangennock, because the carburetted hydrogen 

 Wliich they so abundantly evolve is not supplied with a line quantity of oxy- 

 gen, and lience much of their carbon goes oft" in smoke, and their sub-carbu- 

 retted hydrogen gas in an invisible form. These results are quite accordant 

 with my exiieriments on these coals with my calorimeter. At first, from 

 certain defects in the apparatus, whereby the coals were imperfectly burned 

 and a good deal of smoke was disengaged, I found that the best coals imported 

 into London, such as Lambton's Wallsend, lletton Do. and Pole's Main, 

 afforded a smaller proportion of heat than the Llangennock, or even anthra- 

 cite ; but, when I diminished these defects, 1 obtained much more heat from 

 the Tanfield Moor coal than from the Llangennock, and more from this than 

 from the anthracite. In fact, a coal which, like the Newcastle caking coal, 

 contains 5-239 of hydrogen, is capable of giving out in complete combustion 

 as much heat as if it contained an extra lOJ percent, of carbon ; but, instead 

 of this additional heat, it affords in common furnaces much less heat than the 

 Llangennock, though this is much poorer in the most calorific constituent, 

 viz., the hydrogen. 



It is a remarkable fact, that an inflammable constituent of pit-coal, which 

 is always present, and often inrisibly combined with it to the amount of 5 

 per cent, or more, has never been noticed in any of the ultimate analyses 

 hitherto published. I have examined a great variety of coals from (hfferent 

 parts of the world, and I have seldom found less than 2 per cent, of sulphur 

 lu them. Now, this is a circumstance of great consequence to many manu- 

 facturers, and most essentially to iron-masters. Some of my results upon 

 tbis subject were published in the number of the Athensinmi above quoted. 

 Sulphur in its calorific power ranks low, being, according to Dr. Dalton, one- 

 half of carbon. If we assume its consumptiou of oxygen in combustion as 

 the measure of its heating power, it wiU stand to carbon in the relation of 3 

 to 8 ; for 3 parts of carbon consume 8 of oxygen to form carbonic acid, whUe 

 8 of sulphm- consume 8 of oxygen when they are burned into sulphurous 

 acid. The blacksmith knows well what havoc a sulphurous coal makes among 

 his iron in the forge, rendering it entii'cly rotten. The same operation takes 

 place upon the rivets and plates of steam-boilers, when the sulphur of the 

 coals is merely volatilized, without being mingled with sufficient air to bum 

 it. 



The first operation which coals undergo on being heaved into a common 

 furnace, is distillation, attended with a great absorption of heat, and may be 

 compared to the distillation of sulphur in the process of refining it, for which 

 purpose much external heat is requited. But, if the fumes of sulphur or the 

 coals be, after accension, intermingled with the due quantity of atmospherical 

 oxygen, they will, on the contrary, generate internally from the beginning 

 their respective calorific effects. 



At the outset of ray chemical career I suffered in a painful and dangerous 

 v*ay from the refrigeration produced by throwing some pit-coal into a hot 

 furnace. I was extracting oxygen, for common class experiments, from nitre 

 ignited in a large iron bottle, when, having replenished the fire with coal, the 

 gas became condensed in the bottle so much as to occasion a regurgitation of 

 water into it from the gasometer basin, which water, being instantly con- 

 verted into high-pressure st€am, drove out a quantity of red-hot nitre upon 

 my shoulder and arm, so as to bum not only my clothes, but a very con- 

 siderable portion of my skin. In an experimental furnace, so treated, the 

 heat is greatly damped as long as the hydrogenated vapours and gases are 

 being generated ; and it becomes again effective only when the coals have 

 become nearly charred. Were there a contrivance like your patent invention 

 introduced into the furnace for diffusing atmospherical oxygen through the 

 said vapours and gases, no vexatious refrigeration could ensue from feeding 

 the fire prudently, with common pit-coal ; and the extemal orifice through 

 which this smoke-burning air was admitted, might be closed whenever the 

 fire became clear. 



In the case of great steam-boiler furnaces, for which your patent is espe- 

 cially intended, since these are fed at short intervals, your plan of distributing 

 atmospheric air, in a regulated quantity, by numerous jets, through the body 

 of the gasiform matter, is peculiarly happy, and enable you to extract the 

 whole heat which the combustible is capable of affording. The method also 

 which you have contrived for distributing the air under the surface of the 

 grate will ensure due combustion of the coked coals lying there, without ad- 

 mitting a refrigerating blast to the fire. And, finally, your mode of supplying 

 atmospherical oxygen will prevent the possibility of the carbon of the coals 



* Traite de C'himie Orgauique. Introduction, p. 32. 



escaping in the state of carbonic oxide gas, whereby, at present, much heat is 

 lost in our great furnaces. 



Andrew Ure. 

 1, Charlotte-street, Bedford-si/uare, London, 

 Decem/ier 26, 1840. 



LECOUNT'S HISTORY OF THE LONDON AND BIRMINGH.VM 

 RAILWAY. 



Sir — In your last number you have unintentionally done me an injury, 

 which I have no doubt you will redress by admitting this letter. I allude 

 to your stating that my liistory of the London and Birmingham Railway is a 

 reprint from Mr. Roscoe's. I beg to say this is not the case beyond the 32nd 

 page ; the remainder of my work is what it proposes to be, a history of the 

 railway in question, which Mr. Roscoe's is not beyond page 32 — after that 

 point I had nothing whatever to do with it, principally on the account that 

 it was professing what was not to be performed. My name being connected 

 with it is a perfect hoax upon the public ; I never saw a proof sheet after 

 page 32 ; and I may add that what I furnished for that work, although done 

 under a written agreement, has never got me a sight of sixpence of the pub- 

 hsher's money. Beyond tlie point named it may be just as correctly called 

 my history of the Cock Lane ghost, as my history of the Birmingham rail- 

 way ; I had nothing whatever to do with it except as above explained 



Your obedient servant, 



IVellinyton Road, Birmingham, P. Lecount. 



January 7, 1841. 



[We should regret extremely that any unintentional error of ours should 

 be the means of injuring Lieut. Lecount, for whose public services we enter- 

 tain great respect, perhaps his letter will be deemed a sufficient explanation. 

 —Ed. C. E. & A. JouRy.\L.] 



IMPROVEMENTS ON ECCENTRIC RODS. 



F,g. 1. 



TS h 



Tiij-2 



[We very much regret that, through the inadvertence of our wood 

 engraver, several letters of reference were omitted in Mr. Pearce's 

 diagrams given in last month's Journal ; we have therefore thought it 

 our duty to re-insert them, together with the following communi- 

 cations.] 



Sir — I beg to call your attention to my communication on Eccentrics 

 for working the slide valves of Locomotive Engines, which you were 

 pleased to insert in the last number of your widely circulated Journal. 



On reading the explanation of the engravings, I find that the greater 

 part of the letters of reference are not inserted in the figures ; this 

 omission, I think you will perceive, renders the most important point 

 of the subject unintelligible, and I have, therefore, taken the liberty 

 to apprise you of the same, hoping that you will be induced to correct 

 the deficiency by the insertion of the figures complete in your next 

 number. I also beg to point out the two following typographical 

 omissions. In the 5th line of the 6th paragraph, instead of " Suppose 

 it to be, &c." it ought to have been -'Suppose the crank to be, &c.," 

 and in the 1 Ith line of the last paragraph, instead of "caused to be, 

 &c." it ought to have been " caused not to be, &c." 



I remain. Sir, 



Leeds, Your obliged servant, 



Jan. 13M, 1841. Joun C. Pearce. 



