■292 Analyses of Books. [Aprii.^ 



/, fig. 1, one of the eye-bolls, or arms, which sujiport (he cross bar, e; U is aUo 

 seen at e in Ihe plan of (he retort, fig. 3. In this figure, b is tiic flanch of the re(ort,, 

 and c, the ilonr. 



These few particulars will be sufficient to enable the reader to understand the 

 construction of the re(ort ; its action is as follows: 



Action and Management of the Horizontal Rotary Retort. 



When the retort is healed to the proper temperature for the decomposition of the^ 

 coal, the door is slided down, and the coal-boxes charged with small coal areslided 

 into the retort from the table, M, fig. 2, one by one, so that each box rests firraly 

 Bpon the concentric rings placed between the arms of the retort; the door is then 

 elided up again into i(s place, and rendered air-tight by means of wedges. 



When the whole circle, fig. 3, is thus filled w ith coal-boxes (the coal should be- 

 spread in (he boxes, in layers two or three inches in depth), it is obvious that of all 

 the 12 boxes, four only can he situated directly over the fire-place, while the- 

 remaining eight are placed right and left towards the door of the retort. The coal 

 in the former boxes receives the full effect of the heat (see the plan of the fire flues 

 of the retort, fig. 5), while the remaining eight boxes, to which the fire does not 

 extend, are less heated. The roal in the four boxes which are in the hottest pai*? 

 of Ihe retort becomes rapidly decomposed, » hile the coal in all the other boxes is 

 gradually heated, and consequently deprived only of moisture, ])revious to being 

 subjected to the greatest heat. The box, which is situated under Ihe condensing 

 pipe, H, fig. 2, near the entry door, receives the condensed tar which trickles 

 down the pipe, H. 



Now let us supi>ose (hat the coal in the four boxes over the fire jilace is fully 

 decomposed, which will be the case if SS^ 'bs. of coal are in each box, in tw-o 

 hours, the workman then turns the shaft, E, fig. 2, one-third part of the circumfe- 

 rence of a circle, by pulling towards him by means of an iron hook the nearest iron 

 arm that may happen to be opposite to the door; this moves those boxes which at 

 the commencement of the operation were over the fire-place, towards the coldest 

 part of the retort ; namely, towards the door which is opposite to the fire-place, 

 and a second series, or four of the adjacent boxes, are brought in turn into the 

 hottest part of the retort, or over the fire-place, from w hence the preceding boxes 

 ■were removed. 



When the coal in the second series of boxeshas been two hours in the hottest part 

 of tlie retort, its decomposition will be completed ; the workman therefore turns 

 the shaft again one-third part of a circle, and a third series advances in their place, 

 ■while at the same time the first series becomes situated opposite the entry door of 

 the retort, from whence they may be withdrawn and exchanged for an extra set of 

 trays, ready charged with coal, and placed on the iron table for that purpose. 



In this manner tlie opeiation proceeds. One-third part of the whole charge of 

 coal within the retort is always in the act of becoming decomposed ; another third 

 part is gradually heated, and totally deprived of moisture, previous to its being- 

 exposed to the (empera(ure necessary for its decomposition ; and (he remaining 

 third part placed in the coldest part of (he retort receives that portion of tar,, 

 -ivhich escapes decomposition, and trickles down the perpendicular pipe, in order 

 to be decomposed, when the coal upon which it falls becomes situated over the fire- 

 place. Hence the quantity of tar obtained from one chaldron of Newcastle coal,, 

 ■when decomposed by means of an horizontal rotary retort, seldom amounts to more 

 than 60 or 70 lbs. whereas the same quantity of coal, when decomposed by means- 

 of cylindrical or parallelopipedal retorts, yields never less than from 150 (o 180 lbs. 

 An horizontal rotary retort, 12 feet 6 inches in diameter, and 15 inches high, fur- 

 nishes, in the ordinary way of working, every 24 hours, 15,000 cubic feet of gas,, 

 •when five trays of the retort are charged with three bushels of Newcastle coal. The 

 •weight of Ihe retort is three tons ; its capacity 150 cubic feet. 



The hydraulic valve, above described, serves merely to restore Ihe equilibrioii» 

 between the gas within the retort and the atmospheric air without, previous to the 

 opening of the doorof the mouth of the retort. To effect this, the workman raise? 

 the cup, X, by means of (he chain ; so that the small hole, Y, in the cup, X, be- 

 comes raised out of the tar in the cup, T, ai;d he closes it again when the retort is 

 charged: this operation requires two minutes. We have stated already, that (lie 

 door of the retort is ground air-tight ; and hence it requires no luting. 



