102 SPONTANEOUS RISE OP HOT LIE IN A PUMP. 



pump. T relate UiiS; not because I infer the existence of any 

 trick in the remarkable fact so clearly and fully described by 

 J correspondent, but because it appears to indicate the solution. 

 I have not, however, thought the analogy so perfect as to pre- 

 clude ihe necessity of visiting a soapwork, and of making au 

 experiment which seems altogether to clear up the subject. 



The facts at the soap manufactory were precisely as he de- 

 scribes them ; and very striking indeed, notwithstanding my 

 expectation having been previously raised by R. B.'s description. 

 Ihe course of reasoning suggested by them were as follows : 

 Inferences re- 'ihe lie and melted soap upon the silrface, though strongly 

 specciDg the heated, were not sufficiently so to cause steam to be produced 

 continued rise under the pressure of four feet of fluid, added to that of the at- 

 and flow of che mosphere. But, when a part of this last pressure was taken oft 

 Steam v.'as first ^)' ^^^^ action of the p mp, the fluid in contact with the bottom, 

 pio.'iiced v.a- ^^p^ immediately under the suction-pipe, was enabled to give out 

 vaciuni'of the ''^f-^m 5 ^nd the thin portion of fluid lying between the metallic 

 pump, and edge of the pipe, and the bottom of the boiler, would be more 

 fujm'-l^e^ thin P^*^'-'""'^'^-^ ^^*^'^P°^'^'^ (it being a well-known fact, that such 

 sp. c lew/cea ihin tiims are very readily converted intoste?m, as is strikingly 



the ouuoiTi o. ^[^Q^pj i^y healing water in a glass vessel with a small metallic 



tne .-'jcticn- y t> 15 



pips an 1 of ball or piece of glass lying in it; most of the bubbles seeming 



tiie bcil<?r. jQ spring from these small bodies.) The prosfressive increase 



This rendered r » / t 3 



the cckimn in of steam wlli render the fluid in the pump-barrel irothy and 



the pump liohicr than the dense lie in the boiler; and as soon as the 



liglitcr, and '^ . , . •/:■•, u i 



caused its lise ftJ'iction of its spccinc gravity becomes 50 much as tuat a co- 



tocontiQue, \\iw.\\ oi the whole length of the pump shall be lighter than a 

 column of the dense lie, of no greater length than answers to 

 the depth ot the boiler, this Wa will predominate, and cause 

 the other to ascend without the aid of the pump. Now the 

 iirst devclopement of the steam was effected by the action of 

 the pamp^ in taking off atmospheric pressure ; but as soon as 

 the pump became very hot, and the steam very copious, the 

 pressure of t he inclosed column may be conceived to have become 

 much less than is requisite to allow the continued developement 

 of steam ; and the column being allowed to flow out sideways, 

 instead of ever rising to a counterpoise, the diminished pressure, 

 and also the afllus of the hot frothy lie, becomes permanent. 

 And the velocity of emission will be governed by the height to 

 which the lie is enabled or allowed to rise in the trough above 



the 



