:viR. tredc-old's theory. 



25 



healdng, and tlie waste of fuel enormous. AYhen it did become lieated 

 so as to boil, the vrater flowed over at the top of the open tube. 

 Finding that this plan did not answer liis expectations, Mr. Bacon had a 

 tin model made with boiler and reseiwok, as in the orchnary one of the pre- 

 sent day, but with only one pipe ; and so pertinaciously did he adhere to 

 his favourite theoiy that, till he saw rslr. Atkinson's models in operation 

 at Grove End, he would not behevebut that every useful pm-]^)0se would be 

 effected by one pipe only. 



^ye have been led into this sHglit chgi'ession, because we know the pains 

 that has been taken to deprive 1\h\ Atkinson of the merit of bringing this 

 mode of heating into practice, and to ch^ide the merit between the ^larquis 

 de Chabannes and Tvlr. Eacon, neither the one nor the other having been 

 able to apply it to the purposes to which it is now so generally apphed. 

 The former, as we have aheady stated, acted upon the cUscover^- of Bon- 

 nemain and others, and the latrer neither knew its theory nor apphcarion. 



The most scientific, and at the same time the most clear and compre- 

 hensive explanation of the principles of heating by hot water hitherto 

 pubhshed, is in a communication to the Homcultural Society, and pubhshed 

 in thek Transactions, Vol. TIL, by the late 'Mr. Tredgold the ci^il engineer, 

 which we regi'et that our hniiis v.ill not admit of giving at length. 

 The following quotations from that excellent paper will be found useful. 



^' In order to develope the principles,'' says 'Mi. Tredgold, on which 

 a hot water apparatus acts, we may select the simple case of two vessels 

 placed on a horizontal plain, with two pipes to connect them, the vessels 

 being open at the top, and the one pipe connecting the lower parts of the 

 vessels and the other their upper paits. 



If the vessels and pipes be fiUed with water, and heat be applied to 

 the vessel A, the eflect of heat will expand the water in the vessel A, and 

 its siuface will, in consequence, rise to a higher level (a), the former 

 general level sm-face being b h. The density of the fluid in the vessel A 

 \viil also decrease in consequence of its expansion ; but as soon as the 



