1613.] Scientific Intelligence. 69 



combustion ensues? and why should moistiire be necessary 

 often, as by breathing on it ? In this preparation, either not 

 carrying on the heat sufficiently long to metallize the potash, or, 

 beyond this, to its complete burning oiF, will equally prejudice 

 it. If my idea was correct, as to the colour of the flame, we 

 may have a criterion to judge when to stop."' 



2. " In places where W elter's tubes of safety cannot be had, 

 such an arrangement of Woulfe's ajiparatus as will enable an 

 operator to saturate water with the gases, without danger from 

 absorption, cannot fail of being acceptable. The following plan 

 explains such a method, which supersedes the use of Welter's 

 tubes, and will permit the absence of the operator, without 

 danger from absorption. 



" The tube E is twice bent at right angles, with legs of equal 

 length; one descends to the bottom of the tubulated receiver, 

 A; the other to the bottom of a three-necked bottle, B. In 

 this bottle is placed tlie only tube of safety, F, which is neces- 

 sary, descending about half an inch below the surface of tlie 

 water. » 



The tube G is twice bent, and only perforates the corks, 

 without descending into the bottles B and C. 



" Tiie tube H, bent as before, descends (o the bottom of the 

 bottles C and D. Other bottles may be added at pleasure, con- 

 nected as C and D ; that is, having the tubes near the bottom of 

 each bottle; or, perhaps, rather as represented above. 



If the apparatus is wanted to saturate water with muriatic 

 acid gas, a little water must be put in B, as usual, to absorb any 

 sulphurous acid gas evolved ; C is left empty ; and into D, &c. 

 must be introduced the distilled water to be saturated. 



" If during the absence, or from inattention of t'ne operator, 

 an absorption should take place, the water in B vv'ill pass up the 

 tube E, and be deposited on tlie bottom of the empty receiver. 

 When the orifice of the tube F is exposed, the air will rash into 

 tiie bottle B 5 and by its presence, if the absorption is great, will 

 force the remaining water into the receiver, undi the orifice of. 

 the tube E is exposed, when the air will pass through the tube 

 E, and. rising through the water in the receiver^ restore the 

 eqi-ilibrium. 



A part of the water in bottle D will rise simultaneously with 

 the solution ill B, and pass into C ; but as the tube G does not 



