390 



• KNOV/LEDGE ♦ 



[Nov. 7, 1884. 



now beginning to engage the attention of physiologists as well as 

 physicists." — Entjineerinrj . 



The success of the Health Exhibition was not assured from the 

 outset. But curiosity to know what it would be like helped it in 

 its early days. The opening ceremony was performed to time ; 

 but the inflow of visitors, thi'ough the incompleteness of the ar- 

 rangements and the known arrears, was slack. The third week of 

 May, however, found the public current flowing in on a par with 

 the like period of the year before. From this time forward the 

 popularity of the Healtheries exceeded that of the Fisheries. In 

 June the weekly totals were 154,000, as against 73,000 in the 

 previous year. From June to the end of Jnly the superiority of 

 numbers became still more marked, the weekly totals rising to 

 170,000, as against 94,000 in 1883. In August the average weekly 

 totals were 171,000, as against 115,000. The proportion in Septem- 

 ber rose yet higher, being 187,199 to 107,103. Since then the 

 ratio of the totals has been further increased, the three weeks to 

 October 18th averaging 216,615, against 127,698. The following 

 week's total was 200,575. The grand total of the Fisheries returns 

 was 2,703,051 at its close on October 31st. The grand total of the 

 Health Exhibition returns up to the close amounts to 4,167,683. 



Royal Victoria Coffee Hall, Waterloo-bridge-road, S.E. — 

 On Tuesday, 28th ult., a lecture was given by Mr. J. W. Groves at 

 the above hall on " Plant and Animal Mimics," S. Morley, Esq., 

 M.P., in the chair. The lecturer explained that the mimicry in 

 question was unconscious, and its end was usually either to pro- 

 tect the animal or to enable it to reach its prey unperceived. Thus 

 the lion was the colour of the desert sands, so was the camel. 

 The tiger was striped so as to be hidden among the brownish 

 leaves and stems of the bamboo. The leopard's spots made it 

 diflicult to be seen among the shadows of foliage. Turning 

 to fish, the flounder, sole, and many others were marked and 

 coloured like the sand and shingle. Among birds, the ptar- 

 migan was not only coloured in summer bo like the heather that 

 the dogs pass close to her without perceiving her, but her winter 

 plumage was white like the snow, and the colours of most hen birds 

 were adapted for concealment while they are sitting. But in the 

 insect world protective resemblance was carried to its highest per- 

 fection. The leaf insect was hardly distinguished from the leaves 

 it frequents, and the stick insect, used in the manufacture of arti- 

 ficial flowers. Some insects were protected by having such an 

 unpleasant taste or smell that the birds learned to leave them 

 alone, while others, without the unpleasant taste, were protected 

 by being shaped so like the others that they were mistaken for 

 them. A large number of photographic lantern illustrations were 

 shown. The next lecture will be on Nov. 4 by Rev. W. TuckweU, 

 the subject, " A Bank Holiday among the Hills." Some unusually 

 good ballad concerts have been arranged for the Thursdays in 

 November at the above hall. On Nov. 6 Mdme. Evans Warwick 

 win give the concert, in which the talented Mdme. Adeline Paget, 

 as well as other popular artistes, will take part. 



A FEW days since a little girl, whilst attempting to cross the road 

 in Northgate, Hartlepool, was run down and killed by a steam 

 tramcar. Every effort was made by the driver to warn the child 

 of her danger, but without avaU, and her body was dreadfully 

 mutilated. There is no reason on earth why this sort of result 

 should follow such an accident, and if tramway vehicles were 

 properly guarded it would be impossible ; and such fatal results 

 would not accrue if due and proper precautions were taken by 

 oramway managers. Of late a number of similar fatal accidents 

 have occurred in different parts of the country, and which 

 would not have proved fatal if proper means had been adopted 

 to prevent those who happen to be on the line from passing 

 under the car. At one time no attempt was made to pro- 

 vide cars with any guard by which any obstruction wonld 

 either be carried along or pushed off the rails, instead of being 

 run over. Latterly, on some lines guards have been affixed 

 to cars in certain towns, which would in most cases push 

 a person along or off the rails, but these are not yet attached 

 to all. Considering the nature of tramcar traffic, whether 

 horses or steam motors are employed, it should be considered 

 imperative, if onlj- in the interests of tramway companies, that the 

 best means of preventing fatal accidents should be provided. In 

 very few cases, however, has this been done, and it can hardly be 

 looked upon as less than criminal negligence that this should be the 

 case. A guard which would be effective in preventing even a child 

 from passing under a car or tramway engine from the front could 

 be made by almost any mechanic who might be asked to do it, and 

 it is high time that all tramway companies should be called upon to 

 provide all cars and tramway engines with such a guard. There is 

 nothing to prevent the application of a form of cow-catcher to all 

 tramway vehicles, and it should be within the power of the Board 

 of Trade to call upon all tramway owners to adopt such a thing 

 under compulsion. — Engineer. 



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 AND DIBECTED ENTELOPE BE ENCLOSED. 



WINE COOKERY. 



[1493] — The revelations of Professor M. Williams in your pages 

 are deeply interesting. Will he kindly supplement them by other 

 instructions in elementary analysis of wine ? 



Some years ago I experimented, according to " Griffin's Wine- 

 testing," upon various kinds as to their alcoholic strength, acidity. 

 and saccharine matter ; but that system gives no help in detecting 

 adulterations. So, after reading your articles of the 10th and 

 24th inst., I made a saturated solution of barium chloride in dis- 

 tilled water, and added a little to test-tubes containing different 

 wines. The effect on choice dry sherry was a caution ! Madeira 

 showed only a slight turbidity, hock slightly more, and claret 

 hardly any. Is this substance as good a test for these other wines 

 as for sherry ? And does it follow that there must also be a pre- 

 cipitate in the process of digestion ? 



As to the late ex-Emperor, it was said that his favourite wine 

 was champagne rather than dry sherry ; and I have heard it stated 

 that one danger of the former is that it may be only rhubarb wine 

 in disguise, because that means oxalic acid ; and where much lime 

 (whether in water or in food solids) is taken simultaneonsly, that 

 means a deposit of oxalate of lime, or calculus, the disease to which 

 Louis Napoleon succumbed. Supposing this to be true — of which 

 I know nothing — it wonld seem to be prudent in the male sex to 

 avoid rhubarb as a vegetable altogether. 



There are, no doubt, many of your readers who, like myself, find 

 they are better with a little (a very little) wine, than without ; and 

 Professor Williams would earn our best thanks by telling us how to 

 detect deleterious substances (other than Bulphuric acid) in the 

 wines commonly met with. Yile Pot.ibis. 



COCOA V. TEA. 



[1494] — Supplementary to Mr. Mattien Williams, my own expe- 

 rience of the relative effects of tea and cocoa may be not without 

 interest. Up till about February of the present year it was my 

 custom to take cocoa daily about 5 p.m., falling asleep at nights 

 within half-an-hour of retiring. For seven months after that 

 period (till a fortnight ago, in point of fact) I substituted tea for 

 the cocoa, with the result, as I now know, of inabiUty to attain 

 somnolency within IJ to 2 hours after going to bed. The cause 

 was suggested by certain correspondence which of late has 

 appeared in the pages of Knowledge. It is almost superfluous t 

 add that the cause has been removed ; I have reverted to cocoa- 

 drinking, and once again enjoy a respectable quantum of " tired 

 nature's sweet restorer." John Bell. 



EUCLID'S THEORY OF PARALLELS. 

 [1495] — In your "Chats about Geometrical Measurement," p. 337, 

 line 5 from end, you say that EucUd's 12th Axiom is " no axiom," 

 as " the converse is demonstrated in the 17th Proposition." If 

 this were the logical "converse" of the axiom, so as to follow 

 immediately from it, there would be some absurdity in making the 

 first statement an axiom and the second a theorem. Bat this is not 

 so. The two statements are of the form "allX is Y," and "all 

 Y^ is X ; " and it is so far from being the case that, if one of these 

 be axiomatic, the other is axiomatic, that it may easily happen that 

 one is axiomatic, while the other is not even trae. 



