Image: Illustrations in the book Heat considered as a mode of motion (fig 4 and 5) by John Tyndall

Description: The illustration is taken from John Tyndall's introductory book on the physics of heat, Heat Considered as a Mode of Motion year 1869 edition. The apparatus on the right is a thermopile, which is a sensitive device for measuring temperature changes. In the upper part of the illustration, the box on the left is a locked container of compressed air that has been let stand for a while. When the valve on this box is opened, the compressed air rushes out of the box and moves towards the face of the thermopile. This causes the temperature at the face of the thermopile to decrease. In the lower half of the illustration, the object on the left is a bellows. The motion of the bellows takes in air, compresses it, and pushes the compressed air out through a nozzle towards the face of the thermopile. This causes the temperature at the face of the thermopile to increase. Discussed in the book on pages 42 to 47 and also page 28.
Title: Illustrations in the book Heat considered as a mode of motion (fig 4 and 5) by John Tyndall
Credit: The illustration appears in John Tyndall's book Heat Considered as a Mode of Motion, first published 1863. It has been copied from pages 27 and 28 of the book's 1869 edition online at Archive.org.
Author: John Tyndall
Permission: Public domain on account of its age
Usage Terms: Public domain
License: Public domain
Attribution Required?: No