1845.1 



THE"CIYIL engineer and ARCHITECT'S JOURNAL. 



123 



The " Smoke-coiisuiuinc apparatus" is applied in a variety of forms to dif- 

 ferent kinds of boilers. Instead of cold air, Mr. Chanter introduces jets of 

 warm air behind the bridge of the furnace. 



A PLAN OF FORMING A FIXED BREAKWATER. 

 13y J. Johnston, Esq. 

 The plan is as follows. A series of distinct and separate caissons, each 

 representing in external form one half of the pier of a bridge, with its cut- 

 water presented to the sea, is to be formed in five to six-fatlioni water, ac- 

 cording to any particular locahty. Each caisson is to consist of cast-iron 

 plates of large size, coated with coal-tar in order to prevent corrosion, and 

 bolted together by means of four-inch flanges ; the whole to be tilled with 

 concrete, granite, or other suitable material : the lower part of each caisson, 

 to the height of thirty-two feet, having a foundation platform of wood, to he 

 completed on shore, and, when prepared, to be launched and towed out to 

 its dcstiueil position (as were the caissons of Westminster and Blackfriars' 

 bridges), and then lowered into their linal position : the whole to be secured 

 to tlie bed of the sea by means of cast-iron pdes, driven through tubes of the 

 same material. As tlie upper part of the caisson is put together, so is the 

 interior to be filled up wilh the solid materials : a coping of well-cramped 

 masonry is to be fixed all round each caisson. The weight of each caisson 

 complete would be about -1500 tons, and the Cost of a breakwater on this 

 principle, extending to nearly a mile in length, is estimated at 297,800/. 



IIIGG'S IMPROVED MONOCHORD. 

 In this instrument measurement has been applied to sound, and the actual 

 relation of one tone to another is shewn on an accurately divided scale of 

 two feet. The open note c being precisely the length of the organ-pipe, from 

 which the same sound is obtained, tlie proper and exact length of every 

 organ-pipe may be ascertained. The diatonic and chromatic scales are de- 

 duced by mathematical divisions alone, without the assistance of the ear, but, 

 being tested by that organ, are found to be perfectly correct. It will be 

 seen, by an attentive examination of these scales, that a string being divided 

 into two equal parts gives the octave of the original note ; into three parts, 

 the fifth of the scale ; into four parts the fourth ; five parts will give the 

 major third ; six parts the minor third ; in fact, this investigation thus car- 

 ried out is eminently calculated to aft'ord insight into the nature of concords 

 and discords. The explanation thus far relates to the diatonic and chromatic 

 scales only : the next portion belongs to the enharmonic divisions, and de- 

 monstrates the exact relation of the thirty-two intervals in the octave, to 

 express which the thirteen kevs of the organ or pianoforte are used ; it will, 

 therefore, ptactically explain the meaning of the terra temperament in refer- 

 ence to those instruments, and it will prove the absolute perfection of tone 

 to be expressed by such instruments as the violin and violoncello. The last 

 scale is that marked pianoforte temperament, and is intended for the assist- 

 ance of persons in remote parts, where the aid of a skilful tuner cannot be 

 obtained ; for by it any lady or gentleman possessed of a correct ear, though 

 totally ignorant of the art of tuning, maj^put an instrument into perfect 

 order. The instrument may be said to be capable of facilitating the prac- 

 tice of singing, the teaching of theory, and the tuning of organs and piano- 

 fortes. 



ON A PLAN OF ECONOMISING FUEL IN THE BOILERS OF LOCO- 

 MOTIVE ENGINES. 

 By C. Tetlet. 



The evaporating power of a boiler, observes the author, is dependent 

 chiefly on three causes : — 1. The amount of boiler surface exposed to the 

 reception of heat. 2. (And very materiallyj On the shape of the boiler ; and 

 3. On the intensity of the heat. 



The heat derived from that part of the boiler immediately over and about 

 the tire, I call (according to usage) radiating heat, while the heat derived 

 from the tubes or flues I call carried heat. The improvement in boilers for 

 the rapid evaporation of water, and for the economy of fuel, consists in di- 

 viding the boiler into two or more compartments, of different heating tem- 

 peratures, having channels for feeding the compartments from that or those 

 containing water of a lower temperature.»';The first partition is placed ver- 

 tically over the water-space at the back; of the boiler, the top of which 

 reaches somewhat above the water-line, and the bottom below the level of 

 the firebars, but leaving a passage for the water beneath it. The second 

 partition reaches from the bottom of the tubular part of the boiler to a little 

 above the level of the fire-box-, and removed but a short distance from the 

 first partition. The third partition is placed in the middle of the tubular 

 boiler, and, as the first, runs up above the water-level. A communication is 

 formed for the supply of water by a pipe running from the compartment 

 nearest the chimney-box into the middle compartment, the top of such pipe 

 being fixed just below the water-level, and the bottom thereof at a point 

 near the lower part of the middle compartment. 



" On evaporation taking place, the steam will diffuse itself over the; top of 

 the partitions nearest to the fire-box and that nearest to the smoke-box, so 

 as to maintain the same pressure on the surface of all the water ; thus the 

 water contained over the top, and in the water-spaces at the front, back, and 

 9ide», of the iire>box, i$ all exposed to the direct action of the fire, or to 



radinling heat, and separated from that which receives only.c«;TiV(/ heat. 

 On the other hand, the water contained in that part of the boiler between 

 the partition introduced nearer to the fire-box and the end of the boiler by 

 the smoke-box is exposed only to the reception of carried heat, or heat of a 

 lower temperature than in the part last described ; the consequence is that 

 evaporation commences, first in that part over the fire-box, and, as the water 

 there becomes wasted, more to supply its place passes from the second com- 

 partment down between the two partitions nearest the fire-box. Now, as 

 this feed-water to supply the first division is received from the surface of 

 the water between the partition nearest the fire-box and that nearest the 

 smoke-bnx, it will he charged with heat almost or entirely at the evaporating 

 point before it enters the first compartment, because as the separate particles 

 become heated in the second division above the surrounding portion, they 

 rise to the surface, and, as the middle partition has its upper edge below the 

 water-level, the surface-water passes over it, and descends to the bottom of 

 the fire-box partition and passes under it. As the water leave* the second 

 compartment, either by tvaporation, or to feed the first, that loss-or waste is 

 replaced by water descending from the upper regions of tlie water in the third 

 compartment down the pipe or channel, by virtue of its tendency to preserve 

 its own level. .The third compartment is again fed through another pipe by 

 a force-pump, or other usual means ; this pipe may be joined in any conve- 

 nient part of the said compartment, but it is preferred that it should be at or 

 near the bottom. Any suitable number of partitions may be similarly intro- 

 duced, although in this description of boiler, when of moderate length, I am 

 of opinion that two compartments are enough to serve all purposes of 

 economy. 



If we examine, for the sake of contrast, what takes place in the same 

 boiler when constructed without such divisions, we shall find an operation to 

 take place as follows : the boiler being filled to its proper height with water, 

 and the fire lighted, the water immediately surrounding the fire-box receives 

 its heat with greater rapidity, in the proportion of 3 to 1 of each square foot 

 of the fire-box, as compared with the same extent of the tubular part;, now, 

 ■as each particle of water around the fire-box becomes charged with heat, it 

 becomes specifically lighter, and, therefore, rises into the higher regions, and 

 Intermixes with the water in the tubuIaP|)art, until at the last the whole is 

 brought up to tlie evaporating point. The engine being then set to work, a 

 continual injection of fresh water takes place to supply the loss arising from 

 evaporation. This feed-water, being colder than that already heated in the 

 boiler, is of greater specific gravity, in virtue of which it will find its way to 

 the lowest level in the boiler, namely, around the fire-box. A circulation is 

 thus established by which a current of the coldest portion of water is con- 

 tinuously driven into the spaces around the fire-box, there receiving a sur- 

 charge of heat, the excess of which converts a portion of the water into 

 vapour, whde the remaining portion, not converted into steam', ascends into 

 the tubular part. It is evident that the feed-water by this process is charged 

 with heat to the evaporating point by the fire-box, and not by the tubes; that 

 is all feed- water entering the boUer after the engine is set to work. The 

 tubular part is therefore supplied continuously with water heated in the fire- 

 box. Now the question is, wliftt loss of fuet arises from this ? 



To solve this, let us call to mind the circumstance, that the quantity of 

 beat contained in a pound of steam never varies ; it is always the same in 

 quantity, whatever be the density and temperature of such steam, and about 

 1200" is fully more than the average allowed by difl"erent experimenters. 

 Now let us suppose the feed-water to be injected at a temperature of 60", and 

 also that the steam be drawn off at a pressure of GO lb. per inch, which would 

 give a temperature for the water in the boiler of 305° before evaporation could 

 proceed ; the water in the whole boiler, the tubular part as well as around the 

 fire-box, would have received 305" — 60" for the temperature of the feed- 

 water, or 245° from the fire-box. The water surrounding the tubes being thus 

 charged with heat by the fire-box, till it reaches the temperature of 305°, it 

 could receive no further accession of heat from the tubes, unless their tem- 

 perature exceeded 305" ; but, if the tubes did exceed that temperature, then 

 the water would he ready to abstract the excess above 305'; therefore 305' 

 must always be deducted from the actual temperature of the flues, as waste 

 for heat which is passing into the chimney unabsorbed by the water. But if 

 the operation be reversed, and the feed-water injected at the said tempera- 

 ture of 60°, and kept separated from the water surrounding the fire-box, then 

 it will abstract all. the heat of a higher temperature than 60°. Hence it is 

 evident that 245° more heat is now abstracted from the tubes than was-abr 

 stracted in the former case. In the former ease 245" passed into the chim- 

 ney which is now passing into the water. If this water, which in the last 

 case abstracted 245°from the tubes, be no'v conducted into the spaces around 

 the fire-box, it will require 245^ less to convert it into steam. If a total heat 

 of 1200° is required for its constitution as steam, then deduct 60" from 1200° 

 and we have 1140" as the amount of heat required frt)m the fire-box. If out 

 of 1140° we eflfeet a saving of 245°, we save 21 per cent of fuel. 



By this improvement, therefore, we prevent the deposit of sediment 

 amongst the tubes to the same extent that we remove the evaporation from 

 that part to the fire-box, which latter may be more easily cleaned and re- 

 paired, if constructed with that view. Secondly, we get up steam much 

 more rapidly. Thirdly, we have in .one compartment water free from turbu- 

 lent emotion, in consequence of which the action of a float for regulating a 

 feed-apparatus will be much mor» certain. And, lastly, we kave aa impor. 

 tant saving in fuel. 



