A, Interior view, showing water pyrometer; B, General view, showing regulating apparatus for gas and air.

Methods. The cement blocks tested were made at the laboratories at St. Louis and were stored there in the moist room until about two weeks before they were to be tested, when they were packed in straw in a refrigerator car and, in the case of a batch shipped during the winter, live steam was injected into the car, which was then sealed. Upon reaching Chicago the blocks were removed to the Underwriters' Laboratories and stored in a warm, dry room until tested. The length of this storage was from two to ten days.

This preliminary series of fire tests is being made in the firetest furnace of the Underwriters' Laboratories in Chicago, a sectional plan of which is shown in Pl. XXII, and elevations of which are shown in fig. 7. Pl. XXIII, B, shows a general view of the heating chamber. The valves for regulating the supply of gas and air are shown in the foreground. The motor and fan for the air blast are located in the compartment above the valves. The door through which the gas is lighted and the isinglass peepholes for observing the progress of the tests are shown at the left of the chamber.

The test pieces are laid with fire clay in the opening in the steelframe, fire-brick-lined hanging door shown in Pl. XXIV, A. When the fire clay has hardened, the rolling door is drawn into the furnace by means of a winch, shown at the left of the chamber in Pl. XXIII, B. The door is held in place in the chamber by means of a latch. When the test is completed, the latch releases the door and it is quickly drawn out of the chamber by means of the weight shown near the ground at the right in Pl. XXIII, B, and at the left in Pl. XXIV, A. When the blocks have been placed in the opening, the door has the appearance shown in Pl. XXIV, A. The door is drawn into the chamber, so that it is about 2 feet from the burners. A view of the interior of the fire chamber, showing the burner wall, is shown in Pl. XXIII, A, and at the right in Pl. XXIV, A. Gas is admitted through holes below the floor level. The openings in the brick wall are for the purpose of admitting air to the fire chamber. The piping shown on the face of the wall is a water pyrometer.

The door is fired for two hours, the temperature being kept as nearly uniform over the door as the adjustment of the furnace permits, or within about a 5 per cent variation. The temperature is brought to 925° C. in about thirty minutes, and is maintained at that point one and one-half hours longer.

The temperature of the heating chamber is determined by means of four thermocouples placed symmetrically 6 inches from the back wall of the heating chamber. The temperature of the face of the test pieces is determined by means of six thermocouples symmetrically placed on the face of the blocks, against which the flames

impinge. These thermocouples are laid in fire-clay tubes in the joints, with the points one-sixteenth inch back of the face of the wall, these ends being protected from the direct heat by a coating of fire clay. Readings on all ten couples are taken at intervals of ten minutes by means of an Englehardt galvanometer.

Five thermometers are hung on the back of the wall for the purpose of determining the rate of heat transmission. The bulbs are held against the blocks by covering them with fire clay, which prevents the cooling effects of air currents.

After the door has been subjected to the heat for two hours the gas is turned off and the door is removed from the chamber. In some of the tests the blocks are allowed to cool slowly in air, and in others they are cooled suddenly by water.

The quenching test consists in directing a stream of water against the hot blocks. The door can be run out of the furnace and the water applied in about thirty or forty seconds after the gas has been turned off. The stream is played for five minutes through a 3-inch nozzle at a distance of 20 feet from the door and at a pressure of 50 pounds per square inch. (See Pl. XXIV, B.)

After the blocks tested in the recent series were sufficiently cool they were removed to the Armour Institute, and, by the courtesy of Prof. R. Burnham, in charge, they were tested for transverse and compressive strength, using the same methods as those used at the laboratories in St. Louis.

Form Q is used for recording the results of the fire tests.

Outline of investigations.-The programme for the permeability investigations includes a preliminary series for the purpose of determining the best method of procedure. The subsequent series covers tests on cement mortars and concretes-those treated with waterproofing coatings and those in which different kinds of waterproofing compounds have been incorporated. Different mixtures, consistencies, and thicknesses are used and the specimens are tested at different ages. Tests will be made on specimens treated with