354 Nenv Publications. 



fide walls of the building. FF, the brick-work, made 

 perfeftly water tight. The dotted line G, reprefents the 

 furface of the water when at reft. Let the depth of the 

 water, outfide and infide of the cheft, be eftimated at four 

 feet. When the engine is at work, fhould the preflTure of 

 the air have forced the water down to the dotted line H, 

 3i feet diftant from the line G, and oiily fix inches from the 

 mouth of the cheft, it follows, that the water muft have rifen 

 in the outer building, or cheft, 3!- feet above G, and have 

 its higheft furface nearly at reft at I. In this cafe the ftrength 

 of the blaft is reckoned equal to feven feet of water, or nearly 

 fix inches of mercurv. ITie fpace betwixt the cheft and out- 

 fide building is three feet. When the engine is at reft, and 

 the water has aflumed its level, the quantity of water within 

 the cheft fhould be equal to that viithout. 



Fig. 4. is a ground plan of Fig. 3. The crofs logs on 

 which the ciftern is fupported are dotted within, but drawn 

 full in the fpace betwixt the flange of the cTieft and outer 

 building. The breadth of the flange- tops of the binding 

 bolts, and thicknefs of the metal of the cheft, are alfo drawri. 

 The letters bear a reference to thofe in No. 3. 



NEW PUBLICATIONS. 



Tlye Chemical Pocket-Bool, or Memoranda Cheviica ; ar- 

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V-/N a plan of general arrangement, nearly fimilar to 

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