The Chemistry of Cookery

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. One of the incidental advantages of the _bain-marie_ is that the stewing may be performed in earthenware or even glass vessels, seeing that they are not directly exposed to the fire. Other forms of such double vessels are obtainable at the best ironmongers. I have lately seen a very neat apparatus of this kind, called ‘Dolby’s Extractor,’ made by Messrs. Griffiths & Browett of Birmingham. This consists of an earthenware vessel that rests on a ledge, and thus hangs in an outer