Peel the pears; cut them in two lengthwise, splitting the stem, or they may be left whole if preferred. Place them carefully in jars; fill the jars with a syrup of 30 deg.; cover the jars without fastening the tops. Place the jars in a boiler of warm water, half covering them. Stand the jars on muffin-rings, slats of wood, or something to raise them off the bottom of the boiler, or they will break while cooking. Cover the boiler and cook the fruit until it is tender and looks clear. Remove the jars carefully, fill them completely full, using more hot syrup, or the contents of one of the cooked jars. Adjust the tops and set them to cool where the air will not strike them. Pears may be cooked the same as peaches, but they are such a very tender fruit, it is better to use the method given, as the shape is kept better in this way.