ders, consisting of several narrow cinctures cut into the shaft at the base of the echinus.
An instrument for measuring hights by observing differences in barometric pressures at different altitudes.
Notably, an instrument for determining altitudes by observation of the boilingpoints of water.
It has a watervessel, lamp, and thermometer.
The example shows the instrument and the case in which it is packed for transportation on the back of a tourist or attendant.
Wollaston's apparatus for in measuring hights by the temperature of boiling water has a mercurial thermometer with a very large bulb and a stem, which has a length of one inch for every degree of the scale.
This is read by a vernier to thousandths.
It is found that a difference of barometric pressure of 0.589 inches is equivalent to 1° in the boiling-point, or 530 feet of ascent at moderate elevations.
Tables have been constructed for use with the apparatus, showing the precise elevation corres