24:6 Dr. J. S. G. Thomas on Thermal Effect of a slow 



flowing in the tube, ranging between and 5 cms. per sec. 

 Briefly, the characteristics of the several curves may be 

 summarised as follows : — 



(1) From fig. 2 it is seen that, except in the case of No. 1 

 wire, the temperature of each wire of the series increases 

 with increase in the mean velocity of the air stream, from 

 its initial zero value, until a maximum value of the tem- 

 perature increase is attained in the case of each wire, the 

 temperature increase thereafter decreasing continuously, 

 the temperature of each wire ultimately falling continuously 

 below its normal value with increase in the impressed 

 velocity of the air stream. 



(2) The temperature of No. 1 wire falls off continuously 

 with increase of the impressed velocity of the # air stream. 



(3) The maximum rise of temperature of the various 

 wires increases progressively in the direction of flow of the 

 impressed air stream, and, moreover, the maximum rise in 

 the case of each wire occurs at a value of the impressed 

 velocity which is progressively greater the further the wire 

 in question is removed from the first wire of the series. 

 Thus the maximum rise of temperature in the case of No. 9 

 wire is greater than that of, say, No. 6 wire, and occurs at a 

 greater value of the impressed velocity of the air stream. 



(4) The variation in the values of the velocity at which 

 the maximum temperature rise is attained in the case of 

 the successive wires, is seen to be large in the case of the 

 the leading wires of the series (wires Nos. 1-6, fig. 2) 

 compared with the variation in the case of later members of 

 the series. 



(5) The thermal behaviour of the several wires in the 

 present case enables the wires to be grouped together as 

 follows : — 



(a) Wires Nos. 1, 2, 3, 4, and 5, for which the initial 

 increase of temperature, where it occurs, progressively 

 increases the later the wire occurs in the sequence in 

 the direction of the air-flow. 



(b) Wires 6 and 7, for which the initial rate of in- 

 crease of temperature is approximately constant and less 

 than that for class (a). 



(V) Wires 8, 9, and 10, for which the initial increase 

 of temperature progressively increases as in group (a). 



(d) Wires 10 and 11, in which the initial increase of 

 temperature progressively decreases as in group (b). 



JFote. — In this classification the first member of each 



