302 ANNUAL REPORT 
handling such a delicate instrument. For certain investigations, how- 
ever, adjustment of coal feed or air inlet, endeavoring to fix the most 
favorable working conditions, these instruments in the hands of the 
technically trained men are valuable adjuncts. Other pyrometers, like 
the Chatelier, the Siemens and the air pyrometer, could hardly withstand 
the intense usage in the hot end of the rotary kiln due to the action of 
the volatilized alkali, ash, etc. The Chatelier pyrometer could be used 
in the upper end of the kiln for indicating the fluctuations in temperature 
Fig. 53. Optical pyrometer, of the Wanner type. 
and could be arranged to make automatic records, at the office. By means 
of an automatic switchboard one or two galvanometers could be made 
to serve an entire plant, though, of course, each kiln would require its 
own thermo couple. By using suitable clay shields the couple could be 
sufficiently protected for long usage. But, as has been said before, in 
the hands of untrained men all these instruments are of questionable value. 
For purposes of pyrometrical study the Chatelier pyrometer is preferred 
by the writer to any other. 
REDUCTION OF HEAT LOSSES. 
The heat losses of the rotary kiln may be reduced by the following 
changes : 
1. Lengthening the kiln. 
N 
Utilizing the heat of the waste gases. 
3. Utilizing the heat of the clinker. 
Lengthening the Kiln.—r. This change, though greatly increas- 
ing the cost of the kiln, would bring about the most natural and greatest 
reduction in fuel consumption. This was fully realized by Edison when 
he constructed his kiln 150 feet in length. Owing to the great length 
of the tube the waste gases are compelled to leave it at a low temperature 
and hence part of the heat now wasted is rendered useful. By 
