72 Notes from the Physiological Laboratory 



temporary stoppage in the main jet. This second- 

 ary jet may be readily made from a common brass 

 blow-pipe, bent in the form shown in J, and 

 steadily supported in such manner tjiat its little 

 flame may constantly play immediately above the 

 opening of the main burner. It is usually neces- 

 sary to still further reduce the small opening of the 

 blow-pipe by squeezing it with pliers, or by other 

 means. The secondary flame is fed by a branch, H, 

 from the source of gas-supply. 



The instrument must be protected from touching 

 the base of the containing vessel either by suspen- 

 sion or by the intervention of a plate of cork or 

 other non-conductor. It must also be held steadily 

 vertical, and should always be accompanied by a 

 thermometer to verify its adjustment. It is also 

 well to have each of the exposed surfaces of mer- 

 cury covered by a drop or two of glycerine to pre- 

 vent oxidation. 



