May 18, 1883.] 



KNOWLEDGE ♦ 



297 



which spreads over the vineyards, and, by hinderinfj 

 radiation, protects the -s-ines against the frost." It would 

 be more correct to say that the smoke particles and mois- 

 ture radiate back again much of the heat that would other- 

 wise be lost by the plants. S. 



I 



DEATH AT THE PLAT. 



THE failure to regulate tlie temperature of the theatres 

 of New York results in the kUIing of from two to 

 twenty persons, it is estimat+'d, every night in the year. 

 When the patrons of the drama assemble in most of the 

 theatres, they find the temperature ranging from 50° to 60° 

 Faiir. By the end of the first act it has reached 80°, and 

 before the close of the second act, 90'. The heat then 

 rapidly increases until 100° are scored, and even then 

 scarcely stops. Just at the point of suffocation, the whole 

 audience is hurried out into the cold night-air or rain, the 

 operation of cutting off the gas occupying about one minute 

 and forty seconds. The consequence of this fall of 80" 

 of temperature in the twinkling of an eye is a chill or shock 

 to the system which brings on pneumonia, malaria, fevers, 

 colds, and all sorts of lung diseases. 



Besides the injury to the health, the stifling heat of the 

 theatres is to the spirits most depressing. Many of them 

 being practically air-tight, one feels as if he had been sitting 

 under an exhausted receiver. There being no ventilation, 

 the vitalising properties of tlie confined air are soon ex- 

 hausted. Mental and physical weariness and languor 

 result, and a vacuity of mind and tliought is manifest on 

 both sides of the footlights. In short, the experiment of 

 li\-ing for three or more hours without change of air has 

 not been successful. To prevent death, sickness, physical 

 exhaustion, and mental depression, places of amusement 

 must l)e ventilated, and their temperature regulated. 



The heat at such places should never be allowed to rise 

 al>ove 70° nor fall below 60°. The temperature of the 

 United States Supreme Court-room at Washington is kept, 

 by the order of the Chief Justice and his associates, at 

 68°. This is about the temperature that seems healthiest 

 to average constitutions. To sit in an artificial tempera- 

 ture 5° above or below this is positively unhealthy. And 

 such is the character of all our theatres, \\'ith but two or 

 three commendable exceptions. They must be made habit- 

 able and healthy, and their temperature regulated by law 

 or by public opinion. 



A New Spectrometer. — Professor Clifton, of Oxford, 

 has brought out a new spectrometer. In the ordinary 

 instrument the axis round which the prism turns, and the 

 axis round which the telescope turns, are generally at an 

 angle to each other ; but it is of importance that they 

 should not be inclined in this way, hence Professor Clifton 

 has made them coincident. There is, in fact, only one 

 axis in the new instrument, the telescope, divided circle, 

 and prism plate being fixed on one conical axis turned 

 very true. 



FoRETELLiKG FiREDAMP ESCAPES. — It is well known 

 that the escape of firedamp in mines is intimately associated 

 ■with the height of the barometer, which thus becomes a 

 means of foretelling when such escapes are most likely to 

 occur. But, according to M. de Chancourtois, who has 

 brought the matter before the French Academy, the 

 danger is also increased by strain in the earth's crust 

 causing or opening fissures in the coal, and he therefore 

 proposes to fix sismographic apparatus at the head of every 

 dangerous mine, in order to detect these strains and pro- 

 vide additional precautions against the gas. — Engineering. 



jRrbi'ftDS!. 



TYNDALL ON SOUND.* 



We are glad to see a fourth edition of this valuable 

 •work, the most suggestive and the most interesting treatise 

 on sound in the English language. The work itself is so 

 well known that it should be unnecessary to dwell here 

 upon its merits ; but the new edition contains some impor- 

 tant additions. The descriptions of the telephones of 

 Bell it Edison, and of the microphone and phonograph, 

 will be read with interest e\-en by those who are already 

 well acquainted with all these instruments. We should 

 have liked to have had here Professor Tyndall's opinion as 

 to the probable future of the phonograph. It is well 

 known that the original descriptions of its performances 

 were considerably exaggerated. The sounds which it was 

 said to repeat were repeated in a sense, but verily they 

 were considerably translated. To recognise in them the 

 original words one had " to make-believe a good deal." 

 The microphone is another instrument which promised 

 (one may say it promises) to do much more than it has 

 hitherto performed. We should have been glad if Professor 

 Tyndall had shown how full of promise this instrument is. 



The experiments on the action upon sound (as respects 

 velocity) of soap-bubbles filled (1) with nitrous oxygen, and 

 (2) with hydrogen, are singularly instructive in their 

 bearing on the phenomena of light. The fog-signalling 

 observations have been somewhat amplified, and are ren- 

 dered clearer by the use of maps. Besides these additions, 

 the methods and results of Professor Tyndall's experiments 

 in the " Action of Free Molecules on Radiant Heat," are 

 here set forth, and an explanation of the singular phe- 

 nomenon of " ' Soundless Tones,' observed by General 

 Douane around Fog-signal Stations on the Coast of the 

 United States," is reproduced and illustrated. 



Bridging the Niagara. — The Canada Southern Rail- 

 way Company is said to have closed a contract with the 

 Phojni.x Bridge Company for the construction of a new 

 iron suspension bridge across the Niagara. The bridge, 

 which will be about a quarter of a mile south of the old 

 Suspension Bridge, is to be ready for trains to cross by 

 Sept. 1, 1883, after which date the Canada Southern Com- 

 pany will not use the International Bridge, at Buflalo, or 

 the old Suspension Bridge, and will thus avoid the pay- 

 ment of the heavy tolls hitherto levied. 



LuMiiER IX Canada .\xd tue Uxited States. — It 

 appears that there are no fewer than 15,024 saw mills in 

 the United States, and 637 in Quebec, Ontario, and 

 Manitoba. In these mills during last year, nearly 

 "50,000,000 ft. more timber was manufactured than in 

 the year 1881. Towards the close of the year, moreover, 

 new mills were being built in every direction, so as to be 

 ready for work this spring. Work in the woods has pros- 

 pered in consequence of the favourable weather, and the 

 lumberman looks for an increase of 15 per cent., and even 

 more, if the weather continues to be in good condition for 

 floating the logs down. It is confidently stated that, from 

 all present indications, the production of pine lumber in 

 the North- West for the year 1S83 will be the largest ever 

 known. The prices realised by manufacturers on the 

 stocks sold in 1^81 and 1882 were high, and the business 

 profitable. This fact has given a great stimulus in the 

 direction of the further expansion of the great lumber 

 trade. 



* "Sound." By John Tj'ndall, D.C.L., &c. Fourth Edition, 

 revised and augmented. (London : Longmans & Co., 1883.) 



