"The reason why drained land gains heat, and water-logged land is always cold, consists in the well-known fact that heat cannot be transmitted _downwards_ through water. This may readily be seen by the following experiments: [Illustration: Fig. 97.] "_Experiment No. 1._--A square box was made, of the form represented by the annexed diagram, eighteen inches deep, eleven inches wide at top, and six inches wide at bottom. It was filled with peat, saturated with water to _c_, forming to that depth (twelve and a half inches) a sort of artificial bog. The box was then filled with water to _d_. A thermometer _a_, was plunged, so that its bulb was within one inch and a half of the bottom. The temperature of the whole mass of peat and water was found to be 39-1/2 deg. Fahr. A gallon of boiling water was then added; it raised the surface of the water to _e_. In five minutes, the thermometer, _a_, rose to 44 deg., owing to the conduction of heat by the thermometer and its guard tube; at ten minutes from the introduction of the hot water, the thermometer, _a_, rose to 46 deg., and it subsequently rose no higher. Another thermometer, _b_, dipping under the surface of the water at _e_, was then introduced, and the following are the indications of the two thermometers at the respective intervals, reckoning from the time the hot water was supplied: _Thermometer b._ _Thermometer a._ 20 minutes 150 deg. 46 deg. 1 hour 30 " 101 deg. 45 deg. 2 hours 30 " 80-1/2 deg. 42 deg. 12 " 40 " 45 deg. 40 deg. "The mean temperature of the external air to which the box was exposed during the above period, was 42 deg., the maximum being 47 deg., and the minimum 37 deg.. "_Experiment No. 2._--With the same arrangement as in the preceding case, a gallon of boiling water was introduced above the peat and water, when the thermometer _a_, was at 36 deg.; in ten minutes it rose to 40 deg.. The cock was then turned for the purpose of drainage, which was but slowly effected; and, at the end of twenty minutes, the thermometer _a_, indicated 40 deg.; at twenty-five minutes, 42 deg., whilst the thermometer _b_, was 142 deg.. At thirty minutes, the cock was withdrawn from the box, and more free egress of water being thus afforded, at thirty-five minutes the flow was no longer continuous, and the thermometer _b_, indicated 48 deg.. The mass was drained, and permeable to a fresh supply of water. Accordingly, another gallon of boiling water was poured over it; and, in