280 Hentirig hy the Circulation of Fluids. 



remembered that it is statical, and not elastic as in Mr. 

 Perkins's apparatus, and therefore that the worst that can 

 follow from a leak is the metal running out. The boiler for 

 this apparatus may be very small ; in fact, little more than a 

 large tube. The joints of the gas tubes might be screwed in 

 the common way, those of the exterior tubes might be 

 flanged, and put together with a cement of red lead ground 

 in drying oil, plaster of Paris, and fine iron borings, which 

 sets very hard when exposed to heat, and withal retains a 

 certain degree of elasticity. But these tubes might be brazed 

 together in such lengths as would supersede all joints but 

 those at the glands. 



If this arrangement be not very valuable, from the few 

 occasions for its use, it is, I believe, at least new. The only 

 metal before proposed being mercury, the employment of 

 which is precluded by its expense and volatility. 



I am next about to propose an arrangement for the more 

 economical heating of very extensive ranges of hot-houses, 

 &c., by the circulation of hot water, by burning lime in the 

 same apparatus, and applying the heat usually wasted in 

 slacking it to the warming of the water. 



Mr. Dalton has shown that the heat of lime in the act 

 of being slacked is equal to 400° Fahrenheit; and I have 

 found that, under proper management, a given quantity of 

 lime, in slacking, will raise nearly five times its weight of 

 water from 60° Fahrenheit to the boiling point. For this 

 purpose I propose applying either of the arrangements, 

 J%.82. or 83., whichever may be found more advantageous; and, 

 possibly, no enlarged experiments being tried, much better 

 arrangements than either may be devised. Iw^g. 82., a a are 

 double raised inverted conical vessels, which act alternately 

 as boilers ; their inside, or hollow, is filled with the lime- 

 stone to be burnt, and the fuel. The draught of this kiln 

 (for so the boiler becomes) is downwards through the grates 

 b b, and up round the flues c c c c, &c.; thus also heating the 

 water in the boilers contained in the annular conical spaces 

 d df and carrying it to circulate through properly arranged 

 tubes in the ordinary way. When a charge of limestone is 

 burnt down, it is to be slacked in the kiln, by opening the 

 cocks e e, which permit a flow of water down through the 

 vertical axes, or tubes, ff, which are perforated with nume- 

 rous holes, below the level of the line, and are armed with 

 vanes, or knives, round their circumference ; and, being caused 

 slowly to rotate, by the vanes of a smoke-jack, g, placed in 

 the flue, or by any other suitable means, mix up the water 

 ^nd the lime, and break the lumps of the latter, thus 



