Nov. 9, 1883.] 



KNOWLEDGE ♦ 



285 



to tell the time accurately on a watch which had no minute 

 hand ; but besides the difficulty from this cause there are 

 other difficulties of a very special character. Venus is 

 surrounded by an atmosphere. You see the atmosphere in 

 the ring of light surrounding the planet in Vogel's picture. 

 The sun's rays are refracted through this atmosphere, and 

 they place the observer in a condition of very great embar- 

 rassment, for the edge of the sun is distorted at the moment 

 of contact. 



Another source of difficulty arises from the phenomenon 

 known as irradiation. Venus is a black spot ; the sun is of 

 dazzling brilliancy. This contrast has the effect of making 

 Venus smaller than it ought to appear. A white circle on a 

 black ground appears to be larger than a black circle on a 

 white ground, even though both may really be exactly the 

 same size. The irregularities arising from this cause affect 

 in a marked degree the observations of the transit of Venus. 

 The difficulties may, to a certain extent, be removed by call- 

 ing in the aid of photography. By photography, also, a 

 large number of observations can be secured during the pro- 

 gress of the transit, and thus in some degree compensation 

 is made for the rare occurrence of the phenomenon. 



A grand effort has certainly been made by the British 

 Government, under the skilful direction of Mr. Stone, to 

 give the transit of Venus a fair trial. Expeditions were 

 sent to the West Indies, to South Africa and Madagascar, 

 to Australia, and to New Zealand. The expeditions were, 

 on the whole, very fortunate so far as the weather was con- 

 cerned, and no doubt an approximate value of the sun's dis- 

 tance will be the result. I do not, however, believe that 

 the transit of Venus can be expected to give that distance 

 accurately to one-thousandth part. It is impossible to define 

 the contacts with the precision that would be required. 



Asking and Answering. — Correspondents who are so 

 kind as to interrogate me as to the origin of the expres- 

 sions, " Cleanliness is next to Godliness," " A Skeleton in 

 the Cupboard," " Pouring Oil on the Troubled Waters," 

 " He has Vjurnt his Bridges," and the like, are respectfully 

 referred — (1) to Mr. Wheeler's " Familiar Allusions " ; (2) 

 to Dr. CoV)ham Brewer's " Dictionary of Phrase and 

 Fable " ; (.S) to the same learned author's " Reader's Hand- 

 book " ; (4) to Mr. Eliezer Edwards's " Words, Facts, and 

 Phrases"; and, finally, to A'otes and Qneries. I have 

 repeatedly hinted to my readers that my main business 

 here below is to keep out of St. Pancras Workhouse ; and 

 to that Haven of Rest I should speedily be bound if I 

 tried to answer even a twentieth part of the questions 

 asked me, and which (my early education having been 

 sadly neglected) 1 am wholly unable to solve. — G. A. Sala 

 in the lUnslraled London Neivs. 



The Telkphones of the Wokld. — According to a 

 German statistical periodical, in the year 1882 telephones 

 were in use in the whole world in 303 towns, the sub- 

 scribers numbering 78,808. This number is divided as 

 follows: — Europe, 161 towns with 30,006 subscribers; 

 America, 126 towns, with 17,18.5 ; Asia, 7 towns, with 

 120 ; Australia, 5 towns, with 897 ; and Africa, 1 towns, 

 with 210. The European towns having telo^phones are 

 divided as jllows among the difl'erent countries : — Great 

 Britain, 75 cowns, with 7,287 subscribers ; Germany, 21 

 towns, and 3,613 subscribers; France, 18 towns, and 

 4,437 subscribers ; and Italy, 13 towns, and 5,. 507 sub- 

 scriV)ers. There is, therefore, an average of 424 subscribers 

 for every town in Italy, 247 in France, 172 in Germany, 

 and only 97 in Great Britain. The United States has 112 

 towns with telephone stations, and 41,569 subscribers. 



THE CHEMISTRY OF COOKERY. 



By W. Mattieu Williams. 



I NOW come to a very important constituent of animal 

 food, although it is not contained in beef, mutton, 

 pork, poultry, game, fish, or any other organised animal 

 substance. It is not even proved satisfactorily to exist in 

 the blood, although it is somehow obtained from the blood 

 by special gland>< at certain periods. I refer to casein, the 

 substantial basis of cheese, which, as everybody knows, is 

 the consolidated curd of milk. 



It is evident at once that casein must exist in two forms, 

 the soluble and insoluble, so far as the common solvent, 

 water, is concerned. It exists in the soluble form, and 

 completely dissolved in milk, and insoluble in cheese. When 

 precipitated in its insoluble or coagulated form as the curd of 

 new milk it carries with it the fatty matter, or cream, and 

 therefore, in order to study its properties in a state of 

 purity, we must obtain it otherwise. This may be done by 

 allowing the fat globules of the milk to float to the surface, 

 and then remove them — i.e., by separating the cream as by 

 the ordinary dairy method. We thus obtain in the skimmed 

 milk a solution of casein, but there still remains some of 

 the fat. This may be removed by evaporating it down to 

 solidity, and then dissolving out the fat by means of ether, 

 which leaves the soluble casein behind. The adhering 

 ether being evaporated, we have a fairly pure specimen of 

 casein in its original or soluble form. 



This, when dry, is an amber-coloured translucent sub- 

 stance, devoid of odour, and insipid. This insipidity and 

 absence of odour of the pure and separated casein is note- 

 worthy, as it is evidently the condition in which it exists 

 in milk, but very different from that of the casein of 

 cheese. My object in pointing this out is to show that in 

 the course of the manufacture of cheese new properties are 

 developed. Skim milk — a solution of casein — is tasteless 

 and inodorous, while cheese, whether made from skimmed 

 or whole milk, has a very decided flavour and odour. 



If we now add some of our dry casein to water, it 

 dissolves, forming a yellowish viscid fluid, which, on 

 evaporation, becomes covered with a slight film of insoluble 

 casein, which may be readily drawn off. Some of my 

 readers will recognise in this description the resemblance of 

 a now well-known domestic preparation of soluble casein, 

 condensed milk, where it is mixed with much cream, and 

 in the ordinary preparation also much sugar. The cream 

 dilutes the yellowness, but does not quite mask it, and the 

 viscidity is shown by the strings which follow the spoon 

 when a spoonful is lifted. If a concentrated solution of 

 pure casein is exposed to the air it rapidly putrefies, and 

 passes through a series of changes that I must not tarry to 

 describe, beyond stating that ammonia is given off, and 

 some crystalline substances, such as leucine, tyrosine, ifec, 

 very interesting to the physiological chemist, but not im- 

 portant in the kitohen, are formed. 



A solution of casein in water is not coagulated by boiling : 

 it may be repeatedly evaporated to dryness and redissolved. 

 Upon this depends the practicability of preserving milk by 

 evaporating it down, or "condensing." This condensed 

 milk, however, loses a little ; its albumen is sacrificed, as 

 everybody will understand who has dipped a spoon in 

 freshly-boiled milk and observed the skin which the spoon 

 removes from the surface. This is coagulated albumen. 



If alcohol is added to a concentrated solution of casein 

 in water, a pseudo-coagulation occurs ; the casein is pre- 

 cipitated as a white substance like coagulated albumen, but 

 if only a little alcohol is used, the solid may be redissolved 



