364 THE POPULAR SCIENCE MONTHLY. 



ture ? If you tell her that the water must not boil, she shifts her stew- 

 pan 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 labora- 

 tory, where it is also largely used for " digesting " at temperatures be- 

 low 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 can 

 not, 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, and I recommend the introduction 

 of this apparatus into kitchens where a better apparatus is not obtaina- 

 ble. Some iron-mongers 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. 



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 iron-mongers'. I have lately 

 seen a very neat apparatus of this kind, called " Dolby's Extractor." 

 This consists of an earthenware vessel that rests on a ledge, and thus 

 hangs in an outer tin-plate vessel ; but, instead of water, there is an 

 air-space surrounding the earthenware pot. A top screws over this, 

 and the whole stands in an ordinary saucepan of water. The heat is 

 thus very slowly and steadily communicated through an air-bath, and 

 it makes excellent beef -tea ; but, being closed, the evaporation does 

 not keep down the temperature sufficiently to fulfill the above-named 

 conditions for perfect stewing. At temperatures below the boiling- 

 point evaporation proceeds superficially, and the rate of evaporation at 

 a given temperature is proportionate to the surface exposed, irrespect- 

 ive of the total quantity of water ; therefore, the shallower the inner 

 vessel of the bain-marie, and the greater its upper outspread, the 

 lower will be the temperature of its liquid contents when its sides and 

 bottom are heated by boiling water. The water in a basin-shaped in- 

 ner vessel will have a lower temperature than that in a vessel of simi- 

 lar depth, with upright sides, and exposing an equal water-surface. A 

 good water-bath for stewing may be extemporized by using a common 

 pudding-basin (I mean one with projecting rim, as used for tying 

 down the pudding-cloth), and selecting a saucepan just big enough 

 for this to drop into, and rest upon its rim. Put the meat, etc., to be 

 stewed into the basin, pour hot water over them, and hot water into 

 the saucepan, so that the basin shall be in a water-bath ; then let this 



