Thick cylinders are those in which the thickness is considerable in comparison with the internal diameter. To find the bursting pressure of a thick cylinder, take the produel of (1) the tenacity of the material in pounds per square inch, and (2) the thickness of the cylinder in inches, and divide the pro duct by the sum of (1) the thickness in inches, and (2) the internal radius of the cylinder in inches. Tims a cylinder with an internal radius of 4 inches, and a thickness of 5 inches, if made of cast-iron having a tensile strength of 16, 000 lbs. per square inch, has d bursting pressure of 8888.9 lbs., this being the product of 16, 000and 5, divided by the sum of 4 and 5. B.

Engineer, Duties of the. The ordinary daily duties of an engineer are as follows: On coming in the morning, he should first ascertain the amount of water in the boiler; and. if that is all right, proceed to raise steam, either cleaning and spreading the fire, if it has been banked, or making it up, if it has been hauled. A fire is kindled in the boiler in essentially the same manner as in a stove, wood and shavings first being ignited, and then covered with coal. In starting the fire, it is a good plan to cover the back of the grate with coal, to prevent the passage of cold air through the tubes. In getting up steam, the safety-valve should be raised a little, to permit the escape of air from the boiler. Having got the fire under way, the engineer should wipe off the engine, fill the oil-cups, and make any adjustments that may be necessary, such as tightening keys and screwing up joints or glands of stuffing-boxes, and should see that the cylinder-cocks are open. When steam is raised, he should open the stop-valve and start the engine; after which, if a part of his duty is to attend to the shafting, he should examine and oil it. Then he should get out the ashes, provide a supply of coal, and screen it, if necessary, and proceed to make everything tidy around the engine and boiler. Throughout the day, he should keep a watchful eye on the fire, the water, the steam, and the engine. In managing the fire, care should be taken to have the furnace-door open as little as possible; and, if steam is formed too rapidly, the fire should be regulated by closing the damper and ash-pit doors. In regulating the height of the water, it is a good plan to keep a steady feed, and maintain the height constant. If it is found that the water is falling, the engineer should discover whether it is caused by a leak, or by the refusal of the pump to work. He can tell whether the pump is working by the sound of the check-valve falling after each stroke, or by feeling the feed-pipe or check-valve. A pump will not feed when the temperature of the water is very high, unless it is specially adapted for pumping hot water; and if it refuses to work from this cause, the temperature of the water should be reduced. A pump will not deliver water if the proper valves are not opened, if its passages are choked, or if its packing is defective. It would be necessary to examine the pump at once, and endeavor to discover and remedy the difficulty. If the water falls in the boiler on account of a leak, it can sometimes be temporarily repaired with a plug, or the pump can be run faster, so as to keep up the water until stopping-time. If this is not possible, the fire should be hauled, and the engine allowed to run as long as there is sufficient steam-pressure. In case the engineer finds that the pump is not feeding, and he has a fair supply of water in the boiler, he should at once examine the pump, and endeavor to remedy the trouble without stopping the engine. If he does not succeed, however, before the water falls below the level of the lowest gauge-cock, he should haul the fire, and let the engine run as long as the steam-pressure is sufficient. If he has been called away from the boiler, and on his return finds that the water is below the level of the lower gauge-cock, he should immediately ascertain the steam-pressure, and if it is rising rapidly he should haul the fire at once. If the steam-pressure is about the same as usual, he should examine the pump; and if it is not delivering water, he should haul the fire. If the pump is feeding, he may run it faster, watching the steam-gauge carefully. If the pressure does not fall, he should stop the pump and haul the fire. In any case the engine should not be stopped until the steampressure is considerably reduced. The engineer should be very particular, on finding the water low, to examine the steam-gauge at once; and if the pressure is unusually high, he should haul the lire without delay.

A boiler foams or primes either because it has insufficient steam room, or on account of dirt or grease in the boiler or the f'eedwater. The trouble is often experienced with new boilers, and disappears when they become clean. Priming is dangerous, if much water is carried over with the steam, as it is difficult to maintain the water-level constant, and the engine is liable to be broken by the water in the cylinders. If the trouble is caused by insufficient steam-room, it can sometimes be partially overcome by increasing the steam pressure, and throttling it down to the ordinary working pressure in the cylinder; but the only effectual way is to provide more steam-room. If the priming is due to dirt or grease in the boiler, the engineer should blow off frequently, and clean the boiler every few days. In blowing off, it is well to raise the water-level in the boiler by putting on a strong feed, and then blow down below the level that is ordinarily maintained. It is very often the case that the water-level is higher when the engine is running than it is when none of the steam is being used. The engineer should ascertain how much higher the water rises in such a case, so as to have a proper quantity of water when the engine is stopped. B.