94* OP A NEW STATICAL IAM1*. 



the lamp, and to raife if, in order riot only to prevent the 



difagreeable fliadovv of lamps on the ordinary construction, 



which always produces darknefs in fome part of the apartment, 



but alfo to alter the contraction, and afford the manufacturing 



arlift an opportunity of giving it thofe elegant forms of which 



the inftrument is capable. 



A new lamp I fiiall not (peak of * Keir's hydroftatic lamp, nor of that 



thofe of Kier w ' tn wheel-work by f Carcel, as they are both well known, 



and of Carcel. but confine myfelf to the defcription of this new lamp, and 



which I have confidered with the fame defign as thefe philo- 



fophers. 



Bcfcri -tion with The body of the lamp, Fig. I, confifts of three veffels, 



draw-in* C Aalih, dehh, and bbfg. Thefe may be either cylindrical or 



rectangular, and made of (beet iron, they differ little in height, 



Defcripthn of a and about a line in their diameters, the veffels aahh, and 



■Bwftatica dehh, are joined at their lower edges h h ; — dehh is clofed 



at de; and aahh is -terminated at a a, by a fmall gallery or 



balu tirade by way of ornament. The third veffel bbfg, which 



pafles eafily between tjie other two, is alfo clofed at/g, by a 



plate which projects about three lines ; from the center of this 



there rifes a tube kkll, "to the extremity // of which is fcrewed 



the focket of a common Argand's lamp. In the center of this 



is fixed another tube pq, made of tin, in which the iron wire 



win is placed, and is befides fixed to the plate de, at right 



angles to its furface, the end of the wire is furnifhed with a 



nut and fcrew o o. This wire fcrews to direct the veffel bbfg 



in its motion between the two others, and the pofition of the 



nut is intended to determine the limits of that motion. 



To ufe this lamp, let us fuppofe the nut o o to be fo fixed, 

 that when the vefTei bbfg is at itsgreateff. height, there fhall 

 only remain a fpace of 14- or 15 lines between the two other 

 veilels, that is to fay, a length equal to d b. Now pour mer- 

 cury into the fpace between the two veffels to within the dif- 

 tance of a few lines at de, as to rr ; the edge of the middle 

 veflel will then be immerfed in mercury, and all communica- 

 tion between the infide of this veffel and the outer air will be 

 cut off. And if after having unferewed the focket of the lamp, 

 oil be poured into the inftrument by the aperture 1 1, it will 



* Phil of. Journal, Quarto, III. 467. 

 f Philof. journal, New Series, II. 108. 



occupy 



