As soon as the contents of the basins appear completely dry, they may be transferred to the drying oven. The most satisfactory form is one in which the basins are placed in a closed chamber, surrounded by steam at the atmospheric pressure, and at the same time subjected to a vacuum maintained by a water-jet air-pump; but as this apparatus is somewhat costly, it will probably only be provided in laboratories which make a speciality of such work. Next to the vacuum-oven, an air-oven, heated by a gas-burner, and with its temperature controlled by a mercurial regulator to 100-105° C., gives the best results, and it is also the cheapest; but considerable care and some scientific knowledge are required to work it satisfactorily. In intelligent hands good results may be got from the small “breakfast cooker” gas ovens made by Fletcher of Warrington, which are placed on an iron plate heated by a gas burner, the supply of gas to which is regulated by a thermostat, or mercurial gas-regulator, inserted, together with a thermometer, through holes drilled in the top. The basins must not be placed too near the bottom of the oven, which must be protected by a perforated metal plate supported perhaps one inch above it, to prevent radiation and to distribute the hot air. Any cold air required for ventilation should be admitted below this plate, and care should be taken to exclude the products of the burning gas. Contact of the basins with any heated part of the metal-work should be carefully avoided, and they are best supported on grid-shelves covered with wire gauze or perforated metal, so as to allow of free circulation of air. If perforated zinc is used, it must be well supported, as it is much softened at the temperature used. The least satisfactory appliance in skilled hands, but probably the most easy to work by the inexperienced, is the ordinary water- or steam-oven. It is impossible, in this apparatus, to raise the temperature of the interior fully to boiling point, and below this gambier, quebracho, and other solutions containing catechins (p. 298), dry very slowly. On the other hand, so long as it is kept boiling and supplied with water, the temperature is necessarily constant, and there is no danger of overheating, which easily occurs in ovens heated directly by gas. Such ovens are often fitted with openings at the top for use as a steam-bath. To get the best results, the basins must be as freely exposed as possible to the air in the interior of the oven (in no case must basins be set one inside another, except in the exsiccator for cooling), and little or no ventilation from the outside is required, as only traces of moisture remain after evaporation on the steam-bath; so that, after an hour’s drying, any ventilators may safely be closed. As a good deal of cooling takes place through the door, it is best to protect it with some non-conducting material, such as asbestos millboard, which may be