44 On Mr. Arthur JVoolf's improved Apparatus^ 



than the lower ones, it beuig the reservoir as it were into 

 which the lower ones send the steam, to be thence conveyed 

 auay by the steani pipe or pipes. 'I'he following general 

 direction may be given respecting the quantity of water to 

 be kept in a boiler on my construction : — it ought always to 

 fill not only the lower tubes, but the m.ain cylinder A and 

 the cylinder C to about half their diameter; that is, as high 

 as the fire is allowed to reach — and in no case ought it to 

 be allowed to get so low as not to keep full the necks or 

 branches whicli join the smaller cylinders, marked with the 

 letter c, to the c\ lenders A or C ; for the fire is only bene- 

 ficially employed when applied, through the medium of the 

 interposed metal, to water, to convert it into steam-: that 

 is, the purpose of my boiler would in some measure be de- 

 feated, if any of the parts of tlie tubes exposed to the direct 

 action of the fire should present in their int&rior a surface 

 of steam instead of water, to receive the transmitted heat,' 

 which must more or less be the case if the lower tubes, 

 and even a part of the upper^ be not kept filled with the 

 liquid. 



" As to the construction of the fLirnaces, though that 

 must be obvious from the drawings, it may not be improper 

 here to remark that they should always be so built as to 

 give a long and waving course to the flame and heated air, 

 or vapour, forcing them the more effectually to strike against 

 the sides of the tubes which compose the boiler, and so to 

 give out a large portion of their heat before they reach the 

 chimney : unless this be attended to, there will be a much 

 greater waste of fuel than neccssan' ; and the heat commu- 

 nicated to the contents of the boiler will be less from a 

 given quantity of fuel. 



" My invention is not only applicable to all the uses to 

 which the boilers in common use arc generally applied, but 

 to all of them with much better efTccts than the latter, and 

 can besides be applied to purposes in which boilers, con- 

 structed as they have hitherto been, would be of little or no 

 use. The working of all kinds of steam' engines is one- 

 important application of my invention ; for the ste:mi may^ 

 be raised, in a boiler constructed in the manner before de-* 

 scribed, to such a temperature, and consequently to such 

 an expansive force, as to work an engine even without con- 

 densing the steam, by simply allowing it to escape into- 

 the atmosphere after it has done its office, as proposed bv 

 Mr. James Watt, '.n the specification of his patent, dated 

 January 5, 1765): where he says, engines may be worked- 

 by the force of steam, only, by dischareingi the steam •inlO' 



the 



