Albumen, and gluten are both coagulable by heat; if, therefore, we raise the liquor to the boiling point prior to applying the lime, taking care to remove the scum as soon as it shows signs of breaking, and continuing the boiling until the scum thrown to the surface becomes inconsiderable, we shall find that the albumen and gluten, in coagulating and rising, have carried with them the small particles of woody fibre, the wax, and a large proportion of the coloring matter, and that the lime will now throw down the starch, and any other little impurities remaining in suspension in the liquor, leaving it perfectly clear and bright. Tempering is an exceedingly delicate chemical operation, and I have no hesitation in saying, that on its proper performance depends the quality of the produce. The following simple experiments, which all have it in their power to try, will, if they give themselves the trouble, fully satisfy them of two important points--the superiority of the hot over the cold mode, and the necessity for great attention to the operation of tempering. Let them take a tumbler of cane-juice and a bottle containing lime water, add the latter to the former by drops, pausing and stirring between each, and they will find that, after the addition of a certain quantity, the opaque gummy appearance of the liquor undergoes a change, and the impurities contained in it separate into flakes, which increase in size with each drop of lime added, until they become extinct, and the supernatant liquor perfectly transparent; this is the precise point at which the liquor is tempered, and each drop of lime added after this, causes the flakes to diminish rapidly in size, at last entirely to disappear (being re-dissolved), and the liquor to resume its former gummy appearance; it is, therefore, evident that there should be no such expressions as tempering high or low. The reason why some liquor is so difficult to clean is, that it is either tempered high or low; if it be exactly tempered, the impurities contained in it being entirely separated and thrown out of solution, rise to the surface immediately on the application of heat, and are easily removed; but if there be too little lime, a great portion remains in solution, and if too much, a proportional quantity is re-dissolved; and in either case cannot be removed by any mechanical means. It is, therefore, necessary to have some precise test for the application of lime.