applicalle to Steam 'Engines^ ^c. 43 



over and under the other tubes, till it reaches the chimney B, 

 fig. 4. The wall that divides the furnace may be seen in fig. 3, 

 N,N, and in fig. 6, at N. 



To secure a free communication between the different 

 parts of the boiler, the three tubes of the middle cyhn- 

 der C are connected with those of the two exterior C"'s by 

 two pipes 0. The other ends of tlie tubes caa are each 

 fitted with a cover properly secured and bolted, but which 

 can be taken off occasionally to clean out the boiler. 



In working with such boilers, the water carried off by 

 evaporation is replaced by water forced in by the usual 

 means ; and the steam generated is carried to the place in- 

 tended, by means of tubes connected with the upper part of 

 the cylinder A. 



Mr. Woolf has taken out a patent for this very valuable 

 contrivance. In the specification he has lodged of his in- 

 vention, means are pointed out for applying it to the boilers 

 of steam-engines already in use, by ranging a row of cy- 

 linders below the present boiler, and connecting them with, 

 each other and with the boiler. Directions are also givca 

 for constructing boilers composed of cylinders disposed ver- 

 tically ; but as we consider such an arrangement mferior to 

 the horizontal, and as being introduced, perhaps, chiefly for 

 tlie purpose of preventing his patent from being infringed 

 by evasion, we shall not give any further description of it. 

 We cannot, however, dismiss this article without quotm»;. 

 some of Mr. Woolf's remarks, which may prove ver/ 

 useful. 



** It may not be improper (says he) to call the attention 

 of those who may hereafter wish to construct such apparatr.i 

 to one circumstance, namely, that in every case the tubei 

 composing the boiler should be so combined and arranged, 

 and the furnace so constructed, as to make the fire, the flams 

 and heated air to act around, over and among the tubes, 

 embracing the largest possible quantity of their surface. It 

 must be obvious to any one that the tubes may be made of 

 any kind of metal ; but I prefer cast iron as the most con- 

 venient. The size of the tubes may be varied : but in every 

 case care should be taken not to make their diameter too 

 great ; and it must be remembered, that the larger the dia- 

 meter of any single tube in such a boiler the stronger must 

 it be made in proportion, to enable it to bear the same ex- 

 pansive force as the smaller cylinders. It is not essential, 

 However, to my invention that the tubes should be of dif- 

 ferent sizes ; but I prefer that the upper cylinders, especially 

 the one which I call the main cylinder, should bo laigir 



lh;ia 



