xtiugu 

 n.i the 



220 Scientific Intelligence. 



10. Theory of Luminous Flames. — Dr. Karl Hustmaikn has 

 published an elaborate discussion on this subject, in which he con- 

 cludes that the theory of Davy must 1 .-■ altered, but need not be 

 r< ; 1 L«-e.l by a new hypothesis. From :i discussion of the work of 

 previous observers, and a variety ot experiment- on the diminution 

 and re-toration of luminosity in hydrocarbon flames, and on (he 

 l ^ : |:; " ] " ween flame and burner, he arrives at the following 



(1.) The fact that a gas-flame does no^ rest upon the burner, 

 nor a candle-flame upon the wick, as also the fact that a flame 

 mv, ' r duvetly touches a cold body held within it, is to be ex- 

 plained by the cooling action exercised upon the gas by its sur- 

 • are cooled I hrou-imut a definite 

 •*•«" below their ignition-temperature; the flame is therefore 

 -uished. This conclusion is opposed to that of Glochmann. 

 The very considerable distance noticed between the burner 

 e flame of a gas issuing under high pressure, or mixed with 

 a large column of an indifferent eras, cannot be accounted for on 

 - | ut forward by Benevides. The production of such 

 U her to be traced to the cooling action of the 

 -as and of the outer air, and perhaps more especially to 

 the fact that the velocity of the stream of gas in the neighborhood 

 of the burner is greater than the velocity of propagation of ignitum 

 within the gas. 



(3.) In order that other circumstances conditioning the effect 

 may be removed, the velocity of propagation of ignition must be 

 equal to that of the gas-stream at the point, situated some distance 

 re the flame begins. 

 Determination of the velocity of ignition should be made under 

 these gondii? . ..„{ s ;,„. ( , lhis ma! Tnitude is a 



function of the difference between ignition and combustion tem- 

 peratures, conclusions may be drawn from such experiments 

 regarding: the relations exi-thm; between these points. 



(4.) The velocity of propagation of ignition may be easily deter- 



-: and the numbers 



bo obtained may be regarded as comparative quantitative expres- 



; to ignition of these substances.— Ann. der 



Ghemie elxxxi, II, 129, clxxxii, 1 ; Phil. Man., iii, 1. k C. p. 



II. L>Jbi enn nf Pressure on Combustion — M Waktiia has 

 observed the burning of six stearine candles in tree air and in an 

 iron case under a pressure of i ■<».-, .,; ,,,...,,;,. ,-.->. The'y burned 

 under this pressure with a flame of 9 to 12 cm. Ion", and gave 

 much smoke; their luminous pow< ~ the flame 



issumed a yellowish-red color. The H«.«. BU , J we ight after one 



burning was found to be less than in burning i 



■ 1 i-r n-Mdi 



> of the bi, 



has affirmed i 



that the difference of pressure in Falkland's experiments (on 



