This is a report of test work performed under the auspices of the ASME Special Research Committee on Furnace Performance Factors, and covers the testing of a spreader-stoker-fired furnace. Previous test work was performed on three pulverized-coal-fired furnaces and one gas-fired furnace. In so far as possible the present test work followed the technique developed on the previous tests. Furnace heat absorption was determined by furnace heat balance and also by measuring the surface temperature of the exposed side of the furnace tubes. Part 2 of this paper covers the measurement of furnace heat absorption by the latter method. The test procedure required a series of tests to determine the stack dust loading. Because of the many questions received concerning the results of this portion of the test work the data have been included.