Chemically an examination of the ash of tea-leaves also affords some criteria which may also be utilized for the purpose of identifying the true tea-leaf. For instance, in common kinds of wood, such as oak, deal and pine, the proportion of ash is a few-tenths per cent. of the whole, and by taking wood in its ordinary air-dried condition it contains some 20 to 30 per cent. of moisture. Leaves, on the other hand, contain 10, 20 and even 30 times as much mineral matter, there being doubtless a connection between this abundance of mineral matter and the active chemical changes which take place in the leaves during the growth of the plant. In tea-leaves, therefore, as in leaves in general, the ash amounts to a considerable percentage, usually averaging about 6 per cent., so that a chemical examination of the ash forms an important part of the analysis of tea. The proportion of ash in all teas is tolerably constant, genuine tea rarely yielding so little as 5 and never exceeding 6 per cent. of ash on incineration. Therefore, to determine the amount of ash, weigh a small quantity of the tea in its ordinary commercial state and burn it in a platinum crucible and then re-weigh the resultant ash; by observing a few simple precautions very constant and accurate results are attainable by this method. The crucible should be clean and bright, the lid fitting precisely; an iron triangle, covered with a tobacco pipe may be employed to support the crucible during ignition. The operation is then commenced by igniting the empty crucible, and allowing it to cool, being placed for that purpose on a piece of porcelain or iron, immediately weighing the crucible on becoming cold. Next place one or two grams of tea in the crucible, weighing both together, and ignite over a spirit lamp or good gas-burner, stirring the contents with a platinum wire for a few minutes. When ignition is complete the crucible is covered with the lid, let cool again and immediately weighed a second time. If there is any doubt as to the completeness of the ignition, the crucible must be again ignited, and if there is no difference in weight, the ignition is thereby proved finished. As is obvious, in order to obtain accurate results it is indispensable that the crucible should be in the same condition when it is weighed empty and when weighed with the ash, and this is insured by the preliminary ignition and rapid re-weighing, as above described. The following determinations of the percentages of ash in spurious leaves most used in the adulteration of tea, dried after the manner of tea, may serve to illustrate, the leaves being gathered towards the end of August:— Kind of Leaf. Per cent. of Ash. Ash, 9.40 Plum, 9.90 Willow, 9.34