174 On the Preveiilion of Jir m Conduil Pipei, &c. 



inches long, projecting; from the upper part of it; into thi» 

 tube is screwed the globular vessel gg about ten inches dia- 

 meter, and into this globe is screwed the lube /, about one 

 inch external diameter, having a conical (.,.ening through it 

 a (juarler of an inch on the inside, and half an inch on the 

 outside end of it. In the globe gg is the globular float F, 

 about seven, eight or nine inches diameter, as circumstances 

 may require. This globe carries two spindles or rods, the 

 one projecting downwards about half an inch diameter car- 

 ryiny; the valve o, and the other projecting upwards about 

 •2 inch carrying the valve i; this passes through a guide 

 im, as does the lower rod through the guide 7«7?^; the part 

 of the lower rod that passes through the guide is flat, to 

 prevent it from turning round in the operation of screwing 

 the float F to it. 'i he tube t is provided with a valve v, 

 and weight ji\ nearly equal to the weight of the valve. 



Things being thus disposed, let us suppose water to flow 

 into the pipe AB until it rises to pp, then one half of the 

 diameter 07, will be occupied by air q?-, and therefore 

 only one half of the water which the pipe is capable of 

 conveying would be allowed to pass: but as there is no 

 water in the globe gg, the float F will rest on the guide 

 mm and the valve i be opened through which the air will 

 escape until F is floated by the rising of the water in gg, 

 when the valve i will be shut, and none of the water suf- 

 fered to escape; this operation will be repeated as often as 

 a quantitv of air sufficient to fill gg, is collected. 



The valve v is attached in order to prevent any air from 

 entering the pipe, by the tendency of the water to retire in 

 case a partial interruption in the supply should take place; 

 or in the event of a pipe bursting at a point below that to 

 which this apparatus is affixed. 



In the lube c are two flanches, h and e ; the flanch h is 

 intended to prevent the valve o, and its rod froiri falling 

 into the pipe, and would in many instances (though not in 

 the present) supersede the necessity of the valve v ; (he 

 upper flanch e is to receive the valve 0, and prevent the 

 escape of water, should it be necessary to remove the globe 

 gg, or the tube t, for the purpose of repair, 8:c. 



It is easy to see, that by unscrewing the tube t, the float 

 F would rise and close the valve 0, the same eOect would 

 be produced by unscrewing the globe, or by detaching its 

 upper part, and the pressure of the water would eflectually 

 pievent its opening; as, on several points of the pipes to 

 be used for the above purpose, the pressure will be equal to 

 six or eight atmospheres. 



XXVI. Me- 



