Mabch 30, 1883.] 



KNOWLEDGE 



191 



suggests designs for carpets, walls, and pottery. Another 

 combination affords some tine instances of contrast of 

 bines and greens, relieved by delicate touches of appro- 

 priate tints from the red scale. 



Very (|uiet steel grey and other hues may be obtained 

 by the polarizer, and analyser in certain positions acting 

 upon very thin tilniy crystal groups, such as can be obtained 

 from weak solutions. Many of these look good for nothing 

 until the right position of the prism has been discovered, 

 and they can often be lit up with rich colours by means of 

 the selenitc films. A bluish-grey pattern, slightly relieved 

 by pale browns, now before us, is thus instantly changed 

 to a rich violet, relieved with greens. 



Endless illustrations of chromatic combinations and con- 

 trasts may be obtained in the course of a few hours, and 

 more learnt by them than would be possible by brush and 

 paint experiments in many months. 



Practice in colour seeing makes the eye and brain sensi- 

 tive to delicate gradations of tertiary tints, but it by no 

 means tends to an exclusive pleasure in quiet combinations. 

 The colour sense is imperfect unless rich bright hues afford 

 delight, but they must be carefully harmonised ; and this 

 is a matter of proportion in ((uantities and intensities, as 

 well as of hues. 



Woods in the spring and early summer, where anemones, 

 hyacinths, bears' garlic, and rose campion contrast 

 with many tones of green, the browns and greys of tree 

 trunks, and the red-beech leaves of a former year, display 

 a splendour of colour few artists attempt to rival, and on 

 our Devonshire coasts the sun brings out colours on cliffs 

 and sea profusely gorgeous in brilliancy and depth of tone. 

 Not one twentieth of these things are seen by the unpractised 

 eye ; but the ability to see such things may be acquired on 

 a winter's night Viy the fireside, and with the apparatus 

 named. 



THE CHEMISTRY OF COOKERY. 



VI. 

 By W. Mattieu Williams. 



THOSE who are disposed to bow too implicitly to mere 

 authority in scientific matters will do well to study 

 the history and the treatment which gelatine has received 

 from some of the highest of these authorities. Our grand- 

 mothers believed it to be highly nutritious, prepared it in 

 the form of jellies for invalids, and estimated the nutritive 

 value of their soups by the consistency of the jelly which 

 they formed on cooling, which thickness is due to the gela- 

 tine they contain. Isinglass, which is simply the s^\•im- 

 bladder of the sturgeon and similar fishes cut into shreds, 

 was especially esteemed, and sold at high prices. This is 

 the purest natural form of gelatine. 



Everybody believed that the callipash and callipee of 

 the alderman's turtle soup contributed largely to his pro- 

 verbial girth, and those who could not aflbrd to pay for the 

 gelatine of the reptile, made mock turtle from the gela- 

 tinous tissues of calves'-head and pigs'-feet. The delicacies 

 of the Orient, the edible birds' nests, the sea-slugs. Sec, so 

 highly esteemed for their nutritious properties, are varieties 

 of gelatine. 



About fifty or sixty years ago the French Academy of 

 Sciences appointed a bone-soup commission, consisting of 

 some of the most eminent snvans of the period. They 

 worked for above ten years upon the problem submitted to 

 them, that of determining whether or not the soup made by 

 boiling bones until only their mineral matter remained 

 solid, is, or is not, a nutritious food for the inmates of 



hospitals, &c. In the voluminous report whicli they ulti- 

 mately submitted to the Academy, ijiey decided in the 

 negative. 



IJaron Liebig became the popular exponent of their con- 

 clusions, and \igorously denounced gelatine, as not merely 

 a worthless article of food, but as loading the system with 

 material that demands wasteful etTort for its removal. 



The Academicians fed dogs on gelatine alone, and found 

 that they speedily lost flesh, and ultimately died of starvation. 

 A multitude of similar experiments showed that gelatine 

 alone would not support animal life, and hence the conclu- 

 sion that pure gelatine is worthless as an article of food, and 

 that ordinary soups containing gelatine owed their nutritive 

 value to their other constituents. According to the above- 

 named report and the statements of Liebig, the following, 

 which I find on a wrapper of " Liebig's Extract of jMeat," 

 is justifiable : — " This extract of meat differs essentially 

 from the gelatinous product obtained from tendons and 

 muscular fibre, inasmuch as it contains f*0 per cent, of" 

 nutritive matter, while the other contains 4 or •") per cent." 

 Here the four or five per cent, allowed to exist in the 

 " gelatinous product " (ir. ordinary kitchen stock or glaze) 

 is attributed to the constituents it contains over and 

 above the pure gelatine. 



Subsequent experiments, however, have refuted these 

 conclusions. I must not be tempted to describe them in 

 detail, but only to state the general results, which are, 

 that while animals fed on gelatine soup, formed into a 

 soft paste with bread, lost flesh and strength rapidly, they 

 recovered their original weight when to this same food only 

 a very small quantity of the sapid and odorous principles 

 of meat were added. Thus, in the experiments of Messrs. 

 Edwards and Balzac, a young dog that had ceased growing, 

 and had lost one-fifth of its original weight when fed on the 

 bread and gelatine for thirty days, was next supplied with 

 the same food, but to which was added, twice a day, only 

 two table-spoonfuls of soup, made from horse-flesh. There 

 was an increase of weight on the first day, and " in twenty- 

 three days the dog had gained considerably more than its 

 original weight, and was in the enjoyment of vigorous 

 health and strength." 



All this difference was due to the savoury constituents 

 of the four table-spoonfulls of meat soup, which soup con- 

 tained the juices of the flesh, to which, as already stated, 

 its flavour is due. 



The inferences drawn by IM. Edwards from the whole of 

 his experiments are the following : — " 1. That gelatine alone 

 is insufficient for alimentation. 2. That although insuffi- 

 cient, it is not unwholesome. 3. That gelatine contributes 

 to alimentation, and is sutticicnt to sustain it when it is 

 mixed with a due proportion of other products which would 

 themselves prove insufficient if given alone. 4. That 

 gelatine extracted from bones, being identical with that 

 extracted from other parts — and bones being richer in 

 gelatine than other tissues, and able to afford two-thirds of 

 their weight of it — there is an incontestable advantage in 

 making them serve for nutrition in the form of soup, jellies 

 paste, etc., always, however, taking care to provide a proper 

 admixture of the other principles in which thegelatine-soupis 

 defective, .i. That to render gelatine-soup equal in nutritive 

 and digestible qualities to that prepared from meat alone, 

 it is sufficient to mix one-/onrfh of' ineal-soup vitli three- 

 foiirflis of (jelnline-sonjj ; and that, in fact, no difterence is 

 perceptible between soup thus prepared and that made 

 solely from meat. 6. That in preparing soup in this way, 

 the great advantage remains, that, while the soup itself is 

 equally nourishing with mea1>soup, three-fourths of the 

 meat which would be requisite for the latter by the common 

 process of making soup are saved and made useful in 



