(39 ) 
On to the part A of the flange provided with a screw-thread, we 
screw a brass tube in which two openings e have been cut, and in 
which the stem of the manometer-tube may be fastened by means 
of the wooden stopper A cut in two. Over the wider lower-part 
of the flange, we slide the tube consisting of a narrow and a wide 
piece in which openings have been cut at b, d and also at e, 
and which fits at À round the former tube. By means of a tight ring 
at f the two tubes are kept in a coaxial position. In the wide end 
of the second tube the lower cylinder of the manometer-tube may 
be fastened at « by means of a wooden stopper likewise cut in two. 
The cementing is done in the following way: the manometer-tube 
is heated to a little above the melting-point of the cement, a thin 
layer of which is spread on the tube. In the meantime the steel 
piece with the brass tube screwed on to it is heated also to about 
the same temperature. Then the manometer-tube (in the reversed 
position of fig. 3) is slid into the steel piece, over this the second 
tube is slid and then the halves of the wooden stopper are put in 
their places. In this way the manometer-tube is truly centred and 
the space between manometer-tube and flange is entirely filled up 
with cement. Through the openings we may pour in additional 
cement. After this is solidified we turn the apparatus upside down 
(position of fig. 3) so that the glass-reservoir rests on the collar c 
of cement oozed out. 
The superfluous cement is washed away with benzine. 
For the filling with pure hydrogen I refer to Comm. N°. 27; for 
the revolving of the manometer-tube round the axis of the tube 4, 
in order to shut off the gas by means of mercury admitted before- 
hand into the reservoir, I refer to § 3 of this paper. 
§ 6. Calibration, determination of the volume of the tube and 
measurements of the normal volume of the enclosed gas. In order to 
calibrate the graduated tubes and to determine the volumes of the 
reservoirs, we weld a wider tube with a glass stopeock on to the 
capillary tube where the manometer-tube is to be sealed off. On the 
other side of the stopcock, this wider tube terminates in a fine point. 
After being cleaned and dried the manometer-tube is entirely 
filled with mercury. The calibration and gauging is done by weighing 
the mercury which we let flow out. I will not dwell on these ope- 
rations and the corrections they require as they can better be treated 
of when the observations made are communicated, but here I will 
only mention that in these Operations much time was saved and the 
degree of accuracy was greatly increased by placing the tube in a 
4 
Proceedings Royal Acad, Amsterdam Vol. II. 
