22G 



- KNOWLEDGE ♦ 



[Oct. 12, 1883. 



blood by endosmosis through the delicate membrane of 

 that marvellous network of microscopic blood-vessels which 

 is spread over the surface of every one of the myriads of 

 little upstanding filaments which, by their aggregation, 

 constitute the villous or velvet coat of the ston^ch. In 

 some states of prostration, where the blood is insiiRciently 

 supplied with these juices, this endosmosis is like pouring 

 new life into the body, but it is not what is required for 

 the normal sustenance of the healthy body. 



For ordinary food, all the nutritious constituents should 

 be retained, either in the meat itself or in its liquid 

 surrounding. Regarding it theoretically, I should demand 

 the retention of the albumen in the meat, and insist upon 

 its remaining there in the condition of tender semi-solidity, 

 corresponding to the white of an egg when perfectly 

 cooked, as described in No. 4. Also that the gelatine 

 and fibrin be softened by sufficient digestion in hot water, 

 and that the saline juices (those constituting beef-tea) be 

 fartialhj extracted. I say "partially," because their 

 complete extraction, as in the case of the macerated 

 minoed-meat, would too completely rob the meat of its 

 sapidity. How, then, may these theoretical desiderata be 

 attained ? 



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 albu- 

 men to leathery consistence. This may be shown experi- 

 mentally by subjecting an ordinary beef-steak 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 th<?m. Such an ill-used 

 morsel defies the etlbrts of ordinary human jaws, and is 

 curiously curled and distorted. This toughening and curl- 

 ing is a result of the coagulation, hardening, and shrinkage 

 of the albumen as described in No. 3. 



It is evident, therefore, that in stewing, neither cold 

 water nor boiling water should be used, but water at the 

 temperature at which albumen just begins to coagulate — 

 i.e., about 13-1°, or between this and 160" as the extreme. 

 But here we encounter a serious difficulty. How is the 

 unscientific cook to determine and maintain this tempera- 

 ture? If you tell her that the water mu.st 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, 

 and I recommend the introduction of this apparatus into 

 kitchens where a better apparatus is not obtainable. 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. 



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 obtain- 

 able at the best ironmongers. 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, in- 

 stead 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 fulfil the 

 above-named conditions for perfect stewing. At tem- 

 peratures (lelow (he hoiIinc/-poi7it evaporation proceeds 

 superficially, and the rate of evaporation at a given 

 temperature is proportionate to the surface exposed, irre- 

 spective 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 inner vessel 

 will have a lower temperature than that in a vessel of 

 similar depth, with upright sides, and exposing an 

 equal water surface. A good water-bath for stewing may 

 be extemporised by using a common pudding-basLn (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, d-c, 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 outer water simmer — very gently, 

 so as not to jump the basin with its steam. Stew thus for 

 about double the time usually prescribed in English cookery- 

 books, and compare the result with similar materials stewed 

 in boiling or " simmering " water. 



THE SUN'S DISTANCE.* 



Br Peofessoe E. S. Ball, LL.D., 



Astronomer-Boyal for Ireland. 

 (^Continued from page 199.) 



IT has often been observed that at a meeting of the 

 British Association the proceedings assume a certain 

 tone in harmony with tho.'ie branches of science with 

 which our President for the time being has been specially 

 identified. In recognition of this principle, which is both 

 useful and appropriate, the first method which I shall 

 allude to this evening is the exquisitely beautiful mathe- 

 matical calculation by which the distance of the sun can 

 be elaborated from ordinary observations of the planets 

 systematically conducted at our national observations. This 

 method was foreshadowed in the dynamical theory of 

 Xewton, and was wrought to perfection by Leverrier. It 

 is based upon the great law of gravitation, and is inti- 

 mately connected with the splendid discoveries in planetary 

 perturbation which form so striking a chapter in modem 

 astronomical discovery. There is a certain relation 

 between two quantities, which, at first sight, seem quite 

 independent. These quantities are the mass of the earth 

 and the distance of the sun. It follows from the measure- 

 ments of the intensity of gravitation on the earth's sur- 

 face, and from the known revolution of the earth around 

 the sun, that the sun's parallax has a determined ratio to 

 the cube root of the mass of the earth. There is no un- 



* A discourse delivered at the second general meeting of the 

 British Association at Southport. 



