These facts further suggest the importance of taking measures to prevent, as far as possible, the escape of warmth from the hive. Various precautions are adopted for this purpose. The straw skep is, in itself, a bad conductor of heat, and if made thick and strong, will usually enable the bees to maintain a sufficiently high temperature. Still, in excessively cold seasons, it is advisable to wrap straw hives round with matting, sacking, or some other material, in order still further to guard against chilling. With bar-frame hives several points should be attended to. In the first place, it is a great advantage to have their walls double, with an air-space between them. It is even better to fill this space with cork-dust, saw-dust, bran, or chaff, to prevent any circulation of air between the outer and inner walls. Then, it is important to remove empty combs at the beginning of the cold season, and to confine the bees in as small a space as possible, so that their number, constantly diminishing in winter, may suffice to keep up the necessary temperature. Again, it is of some moment to see that there are no considerable apertures in the coverings of the frames, or in the corners of the hive, by which a current of warm air out of, and cold air into, the hive may be set up. Once more, if cushions of chaff be placed behind the frames, to fill up some of the empty parts of the hive, an additional security will be furnished against the lowering of the temperature. In order still further to prevent separation from the cluster, and unnecessary activity, the most skilled apiarians recommend that, in autumn, holes should be made through the combs, near their tops, to serve as passages from one to another, as they are emptied of honey, without the necessity of the bees going down to the bottoms of the combs, in order to reach the other sides or different combs. Another point of great importance in wintering bees, is the prevention of the moisture, produced by their breathing, from condensing in the hive. It should either be allowed to escape by upward ventilation, as strongly recommended by Langstroth, or by laying over the frames of wooden hives a porous material, which at the same time prevents the escape of heat. Light matting, covered with thicknesses of house-flannel or old blanketing, will answer the purpose very well. The constant evaporation from the upper surface will prevent dampness to any serious degree in the lower thicknesses of material. For ourselves, we prefer the method which most effectually prevents the escape of heat, while also securing that vapour shall not be unduly condensed.