New Form of Mountain or other Barometer. 239 
one end takes the place of the finger ; and the pressure, which from 
its shape can be exerted by the whole hand and wrist to keep it 
in place, will be, in several positions of the tube, of the highest 
convenience. 
The additions, necessary for constituting a mountain barome- 
ter, are shewn in figs. 2 and 3; of which the first is a vertical 
section, and the other a ground plan seen from below, of the ap- 
pliances. 
In fig. 2, is seen surrounding the tube, shewn by dotted lines, 
a steel cylinder, cemented to the tube. ‘The middle part of said 
cylinder is left more massive than either extremity, and is work- 
ed into an octagonal shape to allow its being firmly clamped in a 
vice. The lower extremity is cut Into a screw thread, which fits 
the screw of the inverted, bottomless, iron disk that is to form the 
termination of the tube. This disk is made of a piece of a gun 
barrel. ‘The lower edge of this is also screw-cut, and is fitted 
with the ring seen in fig. 3. The notches in that ring, which 
are also shewn, serve for catching a lever or handle by which the 
ring is screwed up. The single line in fig. 2, between the ring 
and the disk, isa section of the bottom of the sub-cistern; which 
bottom is a plate of Russia-iron, hammered so thin as to be flexi- 
ble, and secured by the ring before mentioned. 
One side of the disk is tapped with a screw-thread and fur- 
nished with a screw, as seen in both drawings, for opening or shut- 
ting off the communication of the atmosphere. As this is only 
opened, when the tube is immersed in the cistern; and as one’s 
fingers should be carefully kept from the mercury, fig. 4 repre- 
sents a tool which I use for unscrewing and screwing: the hook- 
ed end of it, as can be readily imagined, fitting in the hole of the 
handle seen in fig. 3. Inasmuch asa great deal of power can- 
not be exerted with such a tool, the handle is necessary in order 
to tighten up the screw more effectually after the withdrawal of 
the barometer from the cistern. 
I should mention that all the permanent screws—those con- 
necting the disk with the cylinder or collar, and the ring with 
the disk—are laid in a cement, which Mr. Green contrived, and 
which, fusible only at a very high heat, has the property of quick- 
ly hardening. An idea of the tightness thus given to all the 
joints may be formed, when I state that in an experimental ar- 
rangement of this kind, wherein the disk had been turned out of 
