6 



Mr. G. A. Hemsalech on the Relative .Behaviour 



were prepared by drilling holes into plates of brass 3 mm. 

 thick. Of the many different patterns tried only two will be 

 described here, which have proved to be the most useful : — 

 Burner No, 1. — 160 holes o£ 1 millim. diameter each, the 

 centres o£ the holes being 1*5 millim. apart from each other. 

 They are arranged in 8 rows of 20 holes each, consecutive 

 rows being displaced in such a way that the gap between two 

 flames of one row is opposite the flame of the next row 

 (fig. 2). In this way a more even distribution of light is 

 obtained. The relative position of this burner with respect 

 to the direction of observation is indicated in the figure. 



Fig. 2. 



Direction of 

 Qbser vat ion. 



Portion of burner No. 1 enlarged 5 times. 



When a low-pressure gas mixture is employed the cones 

 obtained with this burner form an almost flat and continuous 

 surface with only slight elevations over each hole. Seen end 

 on the cone region presents the appearance of a bright thin 

 line. This burner is therefore particularly suited to studying 

 the spectrum of the explosion region. 



Burner No. 2. — 12 holes of 2 millim. diameter, arranged 

 in two rows of 6 each, the distances between the centres of 

 the holes being 3 millimetres (fig. 3). 



Direction of 

 Ohservat ion. 



Fig. 3. 



r ~ ' "" - 1 



•••••• 



Burner No. 2 enlarged 2± times. 



Whenever necessary the number of holes in either burner 

 can be reduced by closing some of them with asbestos. 



