66 THE SCIENTIFIC PAPERS OF 



cracking of the brickwork was thus avoided. The alternating 

 principle of the furnace gave a remarkable result in the extremely 

 high degree of temperature that could be ultimately attained, as 

 each repetition of the process added something to the previous 

 temperature of the furnace, the heat continually accumulating ; 

 and if the surface were sufficiently covered to prevent loss of heat 

 by radiation, it would be possible by continuing the alternation to 

 attain a temperature far higher than in any existing furnace, and 

 limited only by the materials employed. 



Mr. Siemens had not yet had any long experience of the 

 application of the plan to puddling, but from the results already 

 obtained he thought there was full reason to anticipate its entire 

 success. This case was a peculiar one from the necessity of 

 keeping the puddling door open during the process, the furnace 

 being consequently exposed to the open air ; and some modifica- 

 tions were therefore required in the details, which only the experi- 

 ence of further trials could enable them to get fully matured ; 

 there were also difficulties to be overcome in the working on the 

 part of the men, from the great contrast to the accustomed work- 

 ing of puddling furnaces, so much smaller quantity of fuel and so 

 much less draught being required. Besides the saving in fuel, he 

 expected a decided advantage both in the quantity and the quality 

 of the iron made, by removing the violent draught produced by 

 the intense heat of the chimney in the ordinary puddling furnaces ; 

 the comparatively cold chimney in the new furnace, with the 

 damper lowered to within two inches of the top of the chimney, 

 gave so small a draught that the flame did not cut the iron and 

 waste it as in the ordinary furnace, a higher temperature being 

 obtained with a more quiescent atmosphere. There was also the 

 advantage that no flame or particles of fuel were carried over the 

 surface of the iron, bringing sulphur and other impurities from 

 the firegrate. 



Ashes had. to be cleared out frequently from the regenerators, 

 but they were readily removed through the holes provided for the 

 purpose at the back of the furnace, and the puddler simply raked 

 them out on putting a fresh charge into the furnace. The new 

 furnace was found to puddle the iron in about the same time as 

 the ordinary ones, a charge being brought out about every two hours 

 if the fires were sufficiently attended to. It took rather longer to 



