Pure sap makes the clearest sirup and the lightest-coloured sugar. Every bit of dust, leaves, twigs, or bark that gets into the pail leaves its mark on the sugar even though strained out. So covers on the pails are preferred if one can afford them. Most of the sap runs between nine o'clock in the morning and noon. It has been found by tests that this morning sap has more sugar in it than that which runs later in the day. It is the custom in some places to throw away the ice if the sap freezes. This is very wasteful, for this ice contains about thirty per cent. of the sugar. Of course, melting ice is expensive business so one must try not to let his sap freeze. The sap in the storage jar or tank must not be allowed to get warm, though, as it may sour. It should be boiled as soon after gathering as possible to ensure best results. Maple sap contains other ingredients beside water and sugar. In boiling, the water passes off in steam and the sugar and other solids remain. The changes in colour from clear sap to dark brown sugar is caused by the action of the heat upon the sugar and other substances. All sugar makers know that the lightest coloured sirup and sugar can be made from the earliest run of sap. That is because, as the season advances, more of the lime, potash, magnesia, and other substances are present in the sap. You see the tree does not stop work just because you tap it; and the sap is changing every day until, by the time the buds begin to open, the sap is so changed that it does not make good sugar at all. Water boils when it reaches two hundred and twelve degrees, Fahrenheit, as any thermometer will tell you. In fact, you cannot heat water hotter than two hundred and twelve degrees, for at that temperature the water becomes steam. A mixture of sugar and water will not boil at two hundred and twelve degrees but requires a higher temperature. Therefore, as the water passes off the sap in boiling, and as the amount of sugar per gallon increases, it gets hotter and hotter. It is necessary to watch boiling sap carefully to avoid burning. In making sirup it is important to have it just thick enough to taste right and not so thick that it will granulate. Sirup that weighs eleven pounds to the gallon has long been considered as "just right," and it has been found by testing that if you take the sirup off the fire just as soon as the thermometer registers two hundred and nineteen degrees it will weigh eleven pounds to the gallon and will not granulate. If you take it off when the thermometer says two hundred and sixteen degrees your sirup will be a pretty fair article, but you cannot expect to get as good a price for it, because it has more water in it than there should be in a prime article.