SIMMERING OF WATER. 2[7 



of the fads relating to the boiling of water, concerning which 

 fo much has been laid and written, (bould ftill remain in ob- 

 fcurity, Havi;]g, my (elf, been in the habit of conlidering 

 it as the confequence of a rapid efcape of interfperfed air from 

 the heated water, I requeued he would fay why he thought 

 the phenomenon repugnant to that fuppofition. My friend Particular de- 

 proceeded in reply to ftate, that when water is tirft put on f^ o'f'JJ^^^! 

 the fire, in a metallic veflel, the velTel itfelf gradually becomes ing. 

 lined with bubbles ; that thefe bubbles become detached and 

 rife, fothat the whole farface, or at leaft the bottom, becomes . 

 clear again ; that, foon afterwards a rattling noile is heard, 

 (harp and metallic, which encreafes in loudnefs until it almoft 

 perfectly refembles the pouring of fmall fliot into the vcffel ; 

 that the fluid continues in u ftate of tranquillity and tranf- 

 parency during this ftate ; and laftly, that when the noifft 

 is loudeft the Itate of ebullition fuddenly comes on, the pecu- 

 liar noife of fimmering ceafes all at once, and nothing is heard 

 but the foft and moderate noife of aquatic agitation as long as 

 4lie boiling lafts. 



This account, fo remarkable for its precifion and accuracy. It fcems to anfe 



tliewed clearly that my notion, which I believe is the common ^*'°"' J*^ fudden 



•11 ,• 1 1 ^r 1- , 1- . . production and 



opmion, was ill founded. Alter a liHle medilalion, it ap- condenfation of 



peared evident to me that the noife of iimmering muft arife ^""i* 

 ^"rom the collapfion of fteam bubbles, formed at the bottom 

 of the veflTel, and condenfed almoft inftantly upon their 

 afcent in the fluid not yet heated to the boiling point. In 

 fupport of this opinion I fliewed him a common experiment 

 with the water-hammer. This inftrument, which is made Defcription of 

 and fold by the glafs-blowers and barometer-makers, confifls ^^^ water-ham- 

 of a tube, nearly a foot in length and about three quarters 

 of an inch in diameter, terminating in a globe of about two n. 



inches in diameter ; the other end of the tube being clofed. 

 The outer extremity of the globe ends in a capillary tube, 

 through which as much water has been introduced as rather 

 more than fills the globe itfelf. This water has been boiled 

 in the velTel or inllrument, and at the time of boiling, when 

 all the internal cavity not containing water was filled with 

 iieam to the almoft total exclufion of air, the capillary aper- 

 ture was hermetically clofed. The inflrument thus com- 

 pleted is found when cold to contain water and a fpace nearly 

 vacuous, and the experiment from which it derives its name' 



of 



