consequence a decided downward current of cold air at the window which, if the radiator is on the opposite side of the room, rushes across the floor and is accelerated by the upward current of hot air from the radiator. Such a condition tends very decidedly to make cold currents along the floor. If the radiator be placed under the window the cold drafts are interrupted and the heat more diffused moreover, the upward current from the radiator, the downward current from the window and the leakage drafts, all combine to make a resultant draft of cold air against the side of the radiator which lowers the temperature between the loops and altogether tends to increase the effectiveness of the surfaces very considerably over what would be found in still air.
Direct radiators are often put in recesses under windows and low radiators are sometimes placed under window seats. Such settings, while highly desirable from an aesthetic consideration, decidedly change the effectiveness of the radiator both by shutting off the radiant heat and by lessening the free convection. From some rough experiments the author is led to believe that the ordinary marble top, which is often placed on radiators, will reduce the heating effect from 6 to 15 per cent., depending on the size, kind and height of the radiator; but this is not stated on the authority of a careful comparative test.
