42 METHOD OF RAISING WATEE. 



The principle of If the worm tube were open at the top as ufaal, it is evident 

 '"lied w^TodJcc ^^^*- ^'^ ^^^ ^'*^^'^'" employed for cooling, would require to be 

 a current of raifed by fome mechanic force as high as the fiirface ; fuppofe 



water through a tvv'entv feet. But as this water is not wanted for ufe at that 

 worm tub. . • , • , ... . , , , 



elevation, but is only required to give out its heat, and then 



fall down again ; it is clear that this fall may be applied to 



raife a confiderable portion of what is to follow. Various 



means might be devifed for fuch an application ; the fimpleft 



and moft effedual, no doubt, is that to which Sir A. N. has 



given the preference, namely to convert the whole apparatus 



into a fyphon. 



Defcription of Suppofe the worm tub to be clofed at top; the cold water 



the apparatus, conveyed into it at the bottom from the veflel A, and carried off 



heated at top by the pipe B into the overflowing veflel C. 



Let us fuppofe the level in A to be two feet higher than that 



in C, and a current v/ill be kept up through the whole fluid as 



long as may be defired. 



Whether the It muft occur to the experienced engineer that gas or air 



wou^d prevent or ^''^'^^^'^^P^ ^'""^ the water, efpecially when heated and defended 



impede the from the pretTure of the atmofphere. But this may be obviated 



effedl. ^y attending to a few neceflary circum fiances. Firfi, the 



elevation need not be very great, and lefs gas will efcape ; 



fecondly, the temperature may be kept down by a large 



current through pipes of confiderable diameter ; and thirdly, 



ft is pra6licable by various contrivances, that an interior float 



ftiall give notice when the gas has lowered the furface of the 



water beneath it to a certain point, and this may either warn 



an attendant to pump it out, or it may difcharge an apparatus 



to produce the fame effe6l without the immediate exertion of 



labour each individual time. 



Concerning thefe and other fecondary points, I fliall not, 

 however, enlarge ; having enough to regret from ihe neceflary 

 imperfedion of this defcription, taken from the converfation 

 of the inventor, iniiead of being given in his own words. 



W. N, 



DefcriplioT^ 



