By this process of accumulation the highest possible temperature (only limited by the point at which its materials begin to melt), can be obtained in the furnace chamber, without an intensified draft, and with inferior fuel. It has been found that this furnace is capable of making a ton of crucible steel with _one-sixth_ of the fuel required without it, and that while the temperature of the furnace chamber exceeded 4,000° Fahrenheit, the waste products of combustion escaped into the chimney at 240° Fahrenheit, or very little above the temperature at which water boils in the open air. At the locomotive works of the London and North Western Railway at Crewe, where these furnaces have long been used, it was formerly the practice to lock a piece of pitch pine into the flue leading to the chimney, and if at the end of the week the wood was charred, it was evidence that more heat had been wasted than ought to have been, and the men in charge of the furnace were fined. This all-important national question, the waste of fuel, which in modern phraseology may be truly called the waste of energy, was constantly before the mind of Sir William Siemens, who lost no opportunity, in his public utterances, of impressing his hearers, and that still wider circle which he reached through the medium of the press, with a sense of the weighty consequences which it involved. In an address at Liverpool in 1872, as President of the Institution of Mechanical Engineers, he estimated the total coal consumption of this country at one hundred and twenty million tons, which at 10s. per ton amounted to sixty millions sterling. He strongly asserted that one-half of this might be saved by the general adoption of improved appliances which were within the range of actual knowledge; and he went on to speak of outside speculations, which would lead to the expectation of accomplishing these ends with one-eighth or even one-tenth of the actual expenditure. In 1873 he delivered a famous lecture on Fuel to the operative classes at Bradford, on behalf of the British Association, in which he illustrated how fuel should be used by three examples, typical of the three great branches of consumption: _a_, the production of steam power; _b_, the domestic hearth; _c_, the metallurgical furnace. In connection with the last point he mentioned that the Sheffield pot steel-melting furnace only utilised _one-seventieth_ part of the theoretical heat developed in the combustion, and contrasted with it his own furnace for melting steel. In discussing the question of the duration of our coal supply, he indicated what should be our national aim in the following suggestive and inspiring passage: