192 - «Ui»PLY 6t WdRM TUBS BY fPIE sVi^HOT^* 



The fyphon is not quite two inches wide ; it fifes abojit ^4 

 inches above the refervoir in which it is placed, and the de* 

 fcending column is fix inches longer than the afcending one. 

 The machine is conftrucled with all the parts reprefented in 

 Flatc III. Vol. I. but under a different arrangement. It deli- 

 vers about three pints of water every minute, at 31 inches 

 above the refervoir : the alternations are repeated every five 

 feconds. 

 Its power In In the operation of this machine, a bulk of air equal to 



Mrryirigdown ^j^^gg -^mi^ of water is carried down the defcending column 

 every minute, when the fall i§ only fix inches ; but I am cer- 

 tain from experiment that the fyphon would clear itfelf of a 

 much greater bulk in the fame time. 

 Hertce the In an experiment on the 29th of May 1802, with a fyphon 



worm tub fy- ^f the above dimenfions, and a fall of fix inches, it appeared 

 effedual In car- by a graduated bottle which received the raifed water, that the 

 ryingoffthe fyphon would take a quantity of air equal in bulk to four 

 from^the water, ounces of water at leaft, every three feconds. I think, there- 

 fore, that the fmall quantity of air which will be difengaged 

 from the water in the worm tub at a low temperature, by the 

 operation of the fyphon, with a fall of two or three feet, will 

 be carrieJ off as fall as it is produced, unlefs the pipe be very 

 narrow in proportion to the tub, 



I am. Sir, 



Your*s refpeclfully, 



WILLIAM CLOSE. 



VII. 



An Anfzver to Dr. Wollaston*s Statement, " Of an Im- 

 provement in the Form of Spedacle-Glaffes ." By Mr, VfiL* 

 L I A M Jo N E s , F. Am.P.S, Optician, Holborn, 



Tbefpeaaclc ObSERVING in your Journal for laft Months that Dr. 

 glafles of Dr. W. H. Wollafion, by a paper inferted therein, is attempting 

 wnfured!" *° introduce into the conftruaion of fpedacles, the well known 

 and obfolete form of leps called a menifcus ; I beg leave. Sir, 

 to offer through the channel of your fcientific and impartial 

 record, a few obfervations on his arguments ; and my reafons 

 why I do not confider the contrivance as entitled to any claim 

 either of novelty or improvement. 



Wheu-i 



