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problem under  the  coercion  of  the  policeman’s  to  be  enabled  to  bum  coal  without  smoke,  and, persecutions. They were  open  to  observation from the  bridges  and  the  river  shores,  and  so most  of  them  took  to  using  smokeless  but  not therefore gasless  coal,  and  this  made  some  difference in  the  more  prominent  parts  of  London; but the great  mass  of  kitchen  chimneys — the  grand  producers of  smoke — remained  and  remain  as  before, and probably,  with  no  other  motive  but  coercion to restrain  them,  would  have  remained  smoke-makers  to  the  end  of  time,  for  no  Government officials would  have  compelled  them  to  do  that  in which  they  were  not  competent  to  instruct  them.

Fortunately, self-interest  in  another  direction has led  to  a simple  and  easy  solution  of  the  problem. The great  boiler  question,  how  to  consume fuel with  the  minimum  of  waste,  and  also  with the minimum  of  smoke,  was  long  ago  solved  in Cornwall,  where  the  great  cost  of  coal,  by  reason of distant  transit,  forbade  a profitable  use  of  it — unless without  waste. This was  done  for  upwards of a score  of  years,  and  was  talked  of  as  a sort  of wonder,  and  not  believed  in  by  those  who  used coal at  the  pit’s  mouth,  nor  by  Londoners  to  whom the cost  was  far  less  than  in  Cornwall. But one Mr. Wicksted,  far  and  wide  known  as  an  engineer, having taken  in  charge  the  East  London  Water Works, where  the  chief  business  was  to  pump water to  a great  height,  determined  to  do  it  at  as little  cost  as  possible  for  the  benefit  of  his  employers. So he  visited  Cornwall,  satisfied  himself of the  facts,  and  erected  a powerful  steam  engine at Old  Ford,  in  the  locality  where  once  King Alfred changed  the  course  of  the  Lea  river,  and set the  Danish  ships  a-dry  leaving  them  in  terrorem  like  other  Black  Ravens.

The question  of  preventing  smoke  is  simply  that of mixing  a sufficient  (and  not  more  than  sufficient) quantity of  atmospheric  air  with  the  gases  which are distilled  in  the  process  of  burning. If too much air  be  supplied,  the  heat  will  be  carried  off in waste,  and  possibly  without  generating  smoke, just as  a very  small  fire  may  be  blown  out  and extinguished by  too  large  a bellows. If smoke-producing  coal  be  broken  into  fine  dust,  and gradually and  thinly  scattered  on  a hot  coke  fire, the gases  will  be  rapidly  distilled,  and  if  mixed with atmospheric  air  in  the  right  quantity,  all  the gases will  be  burnt,  producing  a bright  flame,  and the residue  will  be  coke  or  carbon,  which  burns without smoke. This is  merely  the  process  adopted in Cornish  boilers,  mechanism  being  used  to  sift the coal-dust  or  small  coal  on  to  the  fire.

Analyses of  cost  in  processes  of  manufacture are common. Analyses of  cost  in  the  chemistry of kitchen  fires  is  at  best  a rare  process  amongst those interested. Fortunately, a very  large  and influential body  have  become  interested  in  smoke prevention. The legislature  has  forbidden  the burning of  coal  in  locomotive  engines,  and  specified that only  smokeless  fuel  shall  be  consumed. The smokeless fuels  are  anthracite  or  Welsh  coal,  and coke. Anthracite disintegrates  and  falls  through the grate  bars,  and  will  not  answer  when  violently shaken along  a railroad. Coke in  many  cases costs double  the  price  of  coal,  and  as  a ton  of  coke will not  give  out  so  much  heat  as  a tone  of  bituminous coal,  it  becomes  a very  important  matter consequently,  without  waste. Many years  back this was  accomplished  by  Mr.  Dewrance  on  the Grand Junction  Railway; but  as  the  Grand  Junction in  those  days  paid  eleven  per  cent.,  little regard was  paid  to  savings  which  perhaps  involved trouble and  opposition. Lower dividends  have now made  every  source  of  saving  desirable,  and scores of  people  have  been  at  work  to  construct coal-burning locomotives,  Mr. Beattie of  the  South-Western  being  the  earliest  in  the  field. Of course, if the  process  be  complete,  that  which  is  simplest and cheapest  is  preferable. One by  Mr. D. K.  Clark fulfils these  conditions. He makes,  at  little  cost, a novel kind  of  bellows; an  infinitesimal  jet  of high-pressure  steam  from  the  boiler  induces  a violent  rush  of  air. As many  of  these  bellows or openings  are  connected  or  applied  above  the surface of  the  black  coal  through  which  the  gases are distilling,  the  jet  of  steam,  and  consequently of air,  is  contrived  to  pitch  in  any  direction  so  as to  mix  thoroughly  with  the  gases,  in  which  case combustion ensues. If the  mixture  be  not  produced, the  cold  air  may  then  pass  through  these tubes without  consuming  the  gases,  and  with  a diminution  of  steam  production. But so  perfect  is Mr.  Clark’s  arrangement,  that  by  turning  off  or  on the  steam  jets,  smoke  maybe  produced  or  prevented at pleasure.

What is  done  in  locomotives  may  be  done  in house  chimneys,  by  powerful  air  draughts  induced by the  chimney. It is  no  doubt  possible  to  prevent the  generation  of  smoke,  if  not  in  open  fires, in fires  partially  closed  in  a peculiar  manner. Fires are  required  in  dwellings  to  be  used  in  two ways: to produce  warmed  air,  and  to  produce radiant heat. Both are  required  in  kitchens  for boiling water,  heating  food,  baking,  and  roasting. The latter  process  cannot  well  be  achieved  without radiant heat. Again, in  cold  weather  the  general atmosphere of  a house  requires  warming  to  that extent which  is  wholesome  for  breathing; but  a greater  amount  of  radiant  heat  is  required  for  the feet of  persons  of  sedentary  habits,  or  whose circulation is  slow. The heat  which  is  pleasant  to the  feet,  would  be  destructive  to  the  lungs; and the heat  which  can  be  borne  by  the  lungs  would be almost  useless  to  the  feet.

One simple  method  of  preventing  smoke,  is  to feed  the  fuel  from  below,  in  which  case  the distillation carries  the  gases  through  the  hot  fuel; and there  is  no  reason  why  this  principle  should not be  applied  to  kitchen  as  well  as  to  other  fires. But, however,  it  is  sufficient  for  our  present purpose that  smoke  from  bituminous  fuel  can  be prevented; the  details  are  not  necessary  in  this present paper.

We suppose,  then,  a bright  atmosphere — bright as  that  of any  city  where  wood  fuel  is  used,  nay, brighter,  for  wood  also  produces  smoke  very unpleasant  in  a peculiar  state  of  the  atmosphere, as  when  a log  of green  elm  hisses and sputters  at you  in  Paris  in  winter  time. And now  for  my gardens. But where  is  the  space? may be  asked. So may  be  asked,  where  is  the  space  for  a garden in  an  uncleared  forest? The space  for  gardens in  a city  is  equal  to  that  of  the  whole  of  the  city, less  the  streets  and  passages; in  short,  it  is  the