200 REPORTS ON THE STATE OP SCIENCE. 



paper on the radiation in a gaseous explosion, to which more particular 

 reference is made later in this Beport. 



A series of experiments on the temperatures of ignition of hydrogen 

 and oxygen produced by adiabatic compression (according to the sugges- 

 tion of Professor Nernst) has been carried out by Professor H. B. 

 Dixon. It was found necessary to check the descent of the piston 

 mechanically when the ' ignition point ' was reached, instead of allow- 

 ing the flame itself to stop the movement, as in Falk's experiments. 1 

 With quickly-igniting mixtures, such as electrolytic gas, there is little 

 difference between the results obtained with a freely moving and with 

 a checked piston; but with slowly igniting mixtures, such as mixtures 

 of hydrogen and air and mixtures with a large excess of oxygen or of 

 hydrogen, there is a considerable difference between the two methods. 

 Thus, while the compression necessary to fire electrolytic gas agrees 

 closely with that found by Falk, the addition of oxygen was found 

 to lower the ignition-point continuously so far as the experiments were 

 carried. Using the value of 7 deduced from Joly's experiments, Pro- 

 fessor Dixon finds that the ignition-point of electrolytic gas is 557° C, 

 which is in close agreement with the ignition temperature determined 

 by Dixon and Coward last year. 



Professor Dalby is communicating to the Association an account of 

 his measurements by means of an orifice of the air-supply to a gas- 

 engine. This work, while not bearing directly on the matters under 

 discussion by the Committee, will be of considerable assistance to those 

 who have to experiment on gas-engines and desire to determine the pro- 

 portion of air in the charge. Professor Coker has made, and will 

 shortly publish, further measurements of the temperatures in a gas- 

 engine cylinder. The Committee hope to be able to discuss Professor 

 Coker 's experiments at greater length next year. 



The Committee are not aware of any important publications on the 

 Continent or in America (during the past year) which bear directly on 

 their work, though mention should be made of a valuable paper by Hans 

 Schmidt 2 dealing with the radiation from a Bunsen flame. 



On the Radiation from Gases. 



In the first and second Eeports of the Committee reference was 

 made to the part played by radiation in the cooling of the products of 

 an explosion, and to its bearing on the measurements of volumetric 

 and specific heat with which those Eeports were principally concerned. 

 The general question of radiation from heated gases has, however, from 

 the point of view of the Committee, an interest and importance of its 

 own which are sufficient to justify a detailed study of it in its wider 

 aspects. Badiation plays a part comparable with that of conduction 

 in determining the heat-flow from the gas to the cylinder walls in the 

 gas-engine, and it is this flow of heat which is the most important 

 peculiarity of the gas-engine, and to which are chiefly due the leading 



1 ' The Ignition Temperatures of Hydrogen- Oxygen Mixtures,' K. G. Falk 

 [Journ. American Ckem. Soc, vol. xxviii., No. 2, 1906.] ' The Ignition Temperatures 

 of Gaseous Mixtures,' K. G. Falk [Journ. American Chem. Soc, vol. xxix., No. 2, 1907]. 



* Ber. der Deutschen Phys. Ges., 1909, p. 87. 



