It is evident from the principles already expounded that cold extraction takes out the albumen, therefore this must be avoided; also that boiling water will harden the albumen to leathery consistence. This may be shown experimentally by subjecting an ordinary beefsteak to the action of boiling water for about half an hour. It will come out in the abominable condition too often obtained by English cooks when they make an attempt at stewing—an unknown art to the majority of them. Such an ill-used morsel defies the efforts of ordinary human jaws, and is curiously curled and distorted. This toughening and curling is a result of the coagulation, hardening, and shrinkage of the albumen as already described. It is evident, therefore, that neither cold water nor boiling water should be used in stewing, but water at the temperature at which albumen just begins to coagulate—_i.e._ about 134°, or between this and 160° as the extreme. My definition of stewing demands a qualification as regards the albumen. Although this is one of the juices of the meat when cold, it should not be extracted in ordinary stewing, as it is in the maceration for beef-tea, and thereby appear as a scum to be rejected. It should be barely coagulated, and thus retained in the meat in as tender a condition as possible. Being a colloid (see _ante_, page 115) its liability to diffusion is small. But here we encounter a serious difficulty. How is the unscientific cook to determine and maintain this temperature? If you tell her that the water must not boil, she shifts her stewpan to the side of the fire, where it shall only simmer, and she firmly believes that such simmering water has a lower temperature than water that is boiling violently over the fire. ‘It stands to reason’ that it must be so, and if the experimental philosopher appeals to fact and the evidence of the thermometer, he is a ‘theorist.’ The French cook escapes this simmering delusion by her common use of the _bain-marie_ or ‘water-bath,’ as we call it in the laboratory, where it is also largely used for ‘digesting’ at temperatures below 212°. This is simply a vessel immersed in an outer vessel of water. The water in the outer vessel may boil, but that in the inner vessel cannot, as its evaporation keeps it below the temperature of the water from which its heat is derived. A carpenter’s glue-pot is a very good and compact form of water-bath. Some ironmongers keep in stock a form of water-bath which they call a ‘milk-scalder.’ This resembles the glue-pot, but has an inner vessel of earthenware which is, of course, a great improvement upon the carpenter’s device, as it may be so easily cleaned. Captain Warren’s, and other similar ‘cooking-pots,’ may be used as water-baths by removing the cover of the inner vessel.