ILLUMINANTS 9 



right-handed thread, and those for coal-gas a left handed one. It is, therefore, 

 impossible for any employe accidentally to fill a cylinder used for one gas with the 

 other, for the screws will not fit, and cannot be made to do so. In closing these 

 remarks we regret to further add that firms still exist in London who sell both 

 gases cheaper, and as a matter of fact not so pure, who still refuse to adopt these 

 mgemous precautions, which leads us once more very obviously to select the same 

 firm that we have already named, even if it were for this reason alone. 



To resume, no accident can possibly happen when using the " blow-through " jet. 



^^S- 5 Fig. 6 



for, as before stated, using too much oxygen simply causes the light to go out, which 

 is of no serious consequence. 



In all cases regulators must be fitted to the gas bottles. When employed for 

 mixed jets these can be " matched," but even that is not absolutely necessary. The 

 regulator which we have used with never-failing satisfaction is also made by Mr. 

 Beard, who has rendered it after numerous experiments and long experience almost 

 perfection ; we cannot find any fault with it after several years of constant use. 

 A cut is given in Fig. 5 which shows its internal mechanism to depend upon an 

 ingenious arrangement of a "lazy-tongs" design. In Fig. 6 the regulator is shown 

 attached to what is known as a gauge. The object of this additional piece of appa- 

 ratus is to indicate how much gas is contained in a bottle. It must be stated here 

 that no gas " regulator " or " gauge " once used for coal-gas should ever be employed 

 for oxygen ; there are chemical reasons which forbid interchange of this description. 



