Sept. 28, 1883.] 



• KNOWLEDGE • 



105 



Extract of Meat " is beef-tea (or mutton-tea) concentrated 

 by evaporation. 



The juices of lean meat may be extracted very com- 

 pletely without cooking the meat at all, merely by mincing 

 it and then placing it in cold water. 2[aceration is the 

 proper name for this treatment. The philosophy of this is 

 interesting, and so little understood in the kitchen that 

 I must explain its rudiments. 



If two liquids capable of mixing together, but of different 

 densities, be placed in the same vessel, the denser at the 

 bottom, they will mix together in defiance of gravitation, 

 the heavy liquid rising and spreading itself throughout the 

 lighter, and the lighter descending and diffusing itself 

 through the heavier. 



Thus, concentrated sulphuric acid (oil of vitriol) which 

 has nearly double the density of water, may be placed 

 under water by pouring water in a tall glass jar, and 

 then carefully pouring the acid down a funnel with a long 

 tube, the bottom end of which touches the bottom of the 

 jar. At fir^t the heavy liquid pushes up the lighter, and 

 its upper surface may be distinctly seen with that of the 

 lighter resting upon it. This is better shown if the water 

 be coloured by a blue tincture of litmus, which is reddened 

 by the acid. A red stratum indicates the boundaries of 

 the two liquids. Gradually the reddening proceeds up- 

 wards and downwards, the whole of the water changes from 

 blue to red, and the acid becomes tinged. 



Graham worked for many years upon the determination 

 of the laws of this diffusion and the rates at which different 

 liquids diffused into each other. His method was to till 

 small jars of uniform size and shape (about 4 oz. capacity) 

 with the saline or other dense solution, place upon the 

 ground mouth of the jar a plate-glass cover, then immerse 

 it, when tilled, in a cylindrical glass vessel containing about 

 20 oz. of distilled water. The cover being very carefully 

 removed, diffusion was allowed to proceed for a given time, 

 and then by analysis the amount of transfer into the dis- 

 tilled water was determined. 



I must resist the temptation to expound the very in- 

 teresting results of these researches, merely stating that 

 they prove this diffusion to be no mere accidental mLxing, 

 but an action that proceeds with a regularity reducible to 

 simple mathematical laws. One curious fact I must men- 

 tion — viz., that on comparing the solutions of a number of 

 different salts, those which crystallise in the same forms 

 have similar rates of diflusion. The law that bears the 

 most directly upon cookery is that " the quantity of any 

 substance diffused from a solution of uniform strength 

 increases as the temperature rises." The application of this 

 will be seen presently. 



It may be supposed that if the jar used in Graham's 

 diffusion experiments were tied over with a mechanically 

 air-tight and water-tight membrane, that brine or otliL-r 

 saline solution thus confined in the jar could not difluse 

 itself into the pure water above and around it ; people who 

 are satisfied with anything that " stands to reason " would 

 be quite sure that a bladder which resists the passage of 

 water even when the water is pressed up to the bursting- 

 point, cannot be permeable to a most gentle and sponta- 

 neous fiow of the same water. The; true philosopher, 

 however, never trusts to any reasoning, not even mathe- 

 matical demonstration, until its conclusions are verified by 

 observations and experiment. In this case all rational pre- 

 conceptions or mathematical calculations based upon the 

 amount of attrartix-c fon'c exerted between the particles of 

 the dillerent liiiuids are outraged by the facts. 



If a stout, well-tied bladder that would burst rather 

 than allow a drop of water to be squeezed mechanically 

 through it bo partially filled with a solution of common 



washing soda, and then immersed in distilled water, the 

 soda will make its way out of the bladder by passing 

 through its walls, and the pure water will go in at the 

 same time ; for if, after some time is allowed, the outer 

 water be tested by dipping into it a strip of red litmus 

 paper, it will be turned blue, showing the presence of the 

 alkali therein, and if the contents of the bladder be weighed 

 or measured, they will be found to have increased by the 

 inflow of fresh water. This inflow is called endosmosis, 

 and the outflow of the solution is called exosnwsis. If an 

 india-rubber bottle be filled with water and immersed in 

 alcohol or ether, the endosmosis of the spirit will be so 

 powerfully exerted as to distend the bottle considerably. 

 If the bottle be filled with alcohol or ether and surrounded 

 by water it will nearly empty itself. 



The force exerted by 'this action is displayed Ijy the 

 rising of the sap from the rootlets of a forest giant to the 

 cells of its topmost leaves. Not only plants, but animals 

 also, are complex osmotic machines. There is scarcely any 

 vital function — if any at all — in which this osmosis does 

 not play an important part. I have no doubt that the mental 

 effort I am at this moment exerting is largely dependent 

 upon the endosmosis and exosmosis that is proceeding 

 through the delicate membranes of some of the manj' miles 

 of blood-vessels that ramify throughout the grey matter of 

 my brain. But I must wander no further beyond the 

 kitchen, having already said enough to indicate that 

 exosmosis is fundamental to the philosophy of beef-tea 

 extraction, and reserve further particulars for my next 

 paper. 



Postscript. — I feel bound to step aside from the proper 

 subject of these papers to make public acknowledgment of 

 an act of honourable generosity, especially as many hard 

 things have been said concerning American plagiarism of 

 the work of British authors. As everybody knows, we 

 have no legal rights in America, and any publisher there 

 may appropriate as much of our work as he chooses. 

 American leyislalors are responsible for this. Neverthe- 

 less, I received, a short time since, a letter from Mr. E. L. 

 Youmans, of New York, enclosing a cheque for £'20, as an 

 honorarium in consideration of the fact that these papers 

 are being reprinted in the Fojmlar Science Magazine. 

 Shortly before this, a similar remittance was sent from 

 another publisher (Messrs. Funk it Wagnalls), who have 

 reprinted " Science in Short Chapters." These facts 

 indicate that some American publishers have larger organs 

 of conscientiousness than the present majority of American 

 legislators. 



I am told that another American publisher has issued 

 another reprint of " Chemistry of Cookery " without 

 making any remittance ; but, as Mr. Proctor would say, 

 " this is a detail." 



THE ANTIQUITY OF MAX.* 



By W. Pexgelly. 



PREVIOUS to 1858 all geological evidence respecting 

 the antiquity of man was received with apathy and 

 indillerence. Early in the present century the Rev. J. 

 M'Enery discovered flint implements beneath a thick 

 continuous sheet of stalagmite in Kent's Cavern, Torquay, 

 but when he submitted these specimens to Dr. Buckland, 

 then the leading geologist of the day, the latter refused 

 to regard them as evidences of the antiquity of man, 

 but was of opinion they belonged to the ancient Britons, 

 who "had scooped out ovens in the stalagmite," thus 



* Abstract of au adiU-ess delivered at the Bi-itisli Association. 



