41 S Harems Substitute, 4^c, 



thus the receiver, and the exterior bell glass. The interior 

 bell and tube mi^t then be fastened together, by grinding or 

 luting. As yet I have only used lutings of waxed cloth, or 

 cork. It may be proper to point out, that 3 or more concen- 

 tric bell glasses, and 4 or more jars, might be used. The 

 union of the bells, receiver, and tube once eflfected, it is hardly 

 more troublesome to use 3 than 2. When the fluid in the 

 central jar is saturated, this may be emptied and replenished 

 from the middle jar, the latter from the external one. Then 

 supplying the external jar anew, the process maybe continued. 



The other figures are to explain an apparatus on the sitae 

 principle, constructed of hollow, oblong paralellopipeds, dif- 

 fering in length more than in breadth ; so as to allow a ser- 

 pentine tube to wind into the interior, and deliver gas under 

 a vessel shaped like a T. 



Fig. 2. represents a vertical section of the whole as when 

 situated for use.* 



Fig. 3. a vertical section of the lower vessels only. 



Fig. 4. a vertical section of the covers alone. 



Fig. 5. a horizontal section, or ground plan of the lower 

 vessels. The upper vessels are so proportioned as to divide 

 the distances between the lower ones equally. 



It may be well to mention, that this apparatus, from the fa- 

 cility with which it may be cleaned and inspected internally, 

 admits of being made of porcelain or stone ware.t I have had 

 a cylindrical one constructed of the latter material, in which 

 the covers are in one piece, with a tube in the centre for in- 

 troducing gas. The apparatus may be made more efficacious, 

 by drilling a series of small holes round the brims of the bell 

 glasses or covers, so as to cause the gas, instead of passing 

 round the brims in large bubbles, to divide itself into very 

 small ones. By this means it will be more thoroughly inter- 

 mingled with fluid. 



* Excepting, that the covers ought to be so depressed, as that their brims may 

 be lower than" the bottoms of the interior vessels over which they are placed 

 respectively. This is necessary to prevent the gas from escaping, fire it have 

 access to the surface of the fluid beneath those bottoms. 



f The apparatus may also be made of glass bottles, duly proportioned, and 

 cut (truncated) alternately near the shoulder and near the bottom. 



