no 
DR. M ^Y. TRAVERS, MR. G. SEXTER. AND DR. A. JAQUEROD 
downward and was drawn to a fine point, wlilch was sealed. The portions A and B 
of the apparatus were heated, and, when the apparatus was thoroughly exhau.sted, 
the point of the tube E was broken below the surface of some warm mercury in a 
basin. The mercury entered slowly, and, passing through the constriction C, ran 
down into A, whicli was heated sufficiently to boil the licpiid. When the apjDaratus 
was completely filled, the tube was cut through the constriction C', and the small bubble 
of air whicli remained in B ivas replaced by mercury. 
Both the upper chamlier and the limb of the U tube which formed the lower chamber 
Avere set by means of plaster of Paris into brass mounts KK', whicli ivere soldered 
to plates IP, slioAim in section in the drawing. In the case of the upper chamber 
this Aims done after it had been filled AAntli mercury. In setting up the barometer 
the IT tube FG aa^s fir.st fixed to the piece of AAmod L AAdiich supported the instru- 
jiient, and AA^as then filled AAotli mercury. The upper portion Aims then iiiA'erted, the 
open end plunged into the limb F of the U tube, and the brass plate I screAved to 
AA'ooden su]i])ort L. A dish AAms placed beloAA^ the apparatus to catch the mercurA" 
oA'erfloAAnng from F ; finally some of the mercury in the U tube AA’as renioA’ed by 
means of a syphon, so that the surfiice of the mercury in the upper and loAA'er 
chambers appeared as in the figure. 
The scale, AA^liich AA’as jfiaced in front of the barometer, consisted of a piece of 
j'late-glass to AA’hich AA^ere joined, by means of Canada balsam, Iaa’o short scales 
.100 millims. in length and dlA’ided in millimetres. To preA'ent them shifting, 
through the floAving of the cement, they AA’ere further fixed by a binding of copper- 
AA’ire coA’ered AA’itli plaster of Paris at the top and bottom. The scale AA'as compared 
AA’ith a standard scale from the Physikalische Eeichsanstalt at Charlottenburg, and 
afterAAairds at the National Ph 3 "sical Laboratory AA’itli a standard metre (p. 119). The 
temperature of the column of mercuiy AA-as measured by means of a thermometer 
diA’ided to -_4-° G. placed half-AA’ay betAA’een the top and l.Aottoim 
