Thermometers For Comparison should all be placed at a certain height from the ground - they should all fare the north (except those which are required to register the maximum temperature in the sunshine, which should face the south); they should not he influenced by radiated heat, by currents, by reflected heat (such as is communicated from an opposite wall) by absorption of heat from the wall, or wood-work to which the thermometer is attached; and, in short, they should be situated where there is a free passage of air. With regard to the height that a thermometer is placed above the ground, it is ascertained that an inch occasionally makes a difference of a few degrees.