Let us introduce some wort into our flask (Fig. 4); then, after we have fitted an india-rubber tube to the little supplementary tube, let us boil the liquid; the steam, finding an easier exit through the india-rubber opening than through the drawn-out tube, will rush out through the india-rubber tube, and thus, as it passes, destroy any germs which may be adhering to the sides of the little supplementary tube. If we close the india-rubber tube by means of a glass stopper, the steam will immediately issue through the bent tube. On permitting the flask to cool, it will then be ready for impregnation. If there were any fear that some foreign germ of an unknown nature might have effected an entrance during cooling, or had not been destroyed by the steam (which is always a little super-heated, in consequence of the resistance which it meets in escaping), we need only place the flasks on a warm stove, and leave them there for a few days or a few weeks to ascertain whether the liquid in them has undergone any change. We should then only use those flasks which contain a sound liquid. At the same time we must warn our readers that this cause of error does not exist once in a thousand times, especially if we use an asbestos stopper to prevent the entrance of little insects which are attracted by the odour of the liquid, and which instinctively seek to enter at the extremity of the tube, and to pass through it into the flask. In going so far, and incurring such labour in search of their food, they condemn themselves to certain death, for they are sure to be drowned, since it would require an intelligence superior to that which they possess to enable them to get out of the flask; the liquid, morever, could not fail to undergo some change, in consequence of the particles of dust that the insects would introduce into it.