March 4, 1875] 



NATURE 



349 



whence the smaller star was in the south-preceding quad- 

 rant. In addition to the authorities for magnitude quoted 

 by Herr Falb, it rcay be mentioned that both components 

 are found in the last Greenwich Catalogue (1864) ; the 

 preceding star is there called 8 mag., and the following 

 one 7. If we transform the differences of R.A. and 

 N.P.D. in this catalogue into angle and distance, there 

 results for about 



1866 '95 Angle 224°-5 Distance 36"'4 

 agreeing as closely with Struve's measures as could be 

 expected. The principal or following component of 

 2 747 is Bradley 801, and its position for the beginning 

 of the present year is in R.A. jh. 28m. S4s'4, and N.P.D. 

 96° 5' 39" ; it is 8' distant from t Orionis, on an angle of 

 225". 



The V.A.RIABLF. Star R Hypr.e. — Observations of this 

 star in southern latitudes are much needed for affording a 

 better insight into the law of variation than we yet possess. 

 That the period has greatly diminished since the time of 

 Maraldi is beyond doubt ; Schonfeld makes it about 500 

 cidys for the year 170S, 487 days for 1785, and 437 days 

 fdi' 1870. It was pointed out by Argelander that good 

 cothparison stars are too low for favourable observation 

 iii central European latitudes. According to the formula 

 iiivolving E= and E^, given in Schonfeld's last catalogue, 

 d maximum wou!d occur on the 25th of February, and 

 the following one falls 1876, May 10. The minimum, 

 v^hich by Schmidt's observations occurs 2co days before 

 iKe maximum, will not be observable in the present year. 

 At greatest brightness the star is found to vary from 4'o 

 to 5-5. Its position for 1875 is in R.A. I3h. 22m. 53s,, 

 and N.P.D. ii2°38'-o. 



WiNNECKE's Comet. — This body is now beyond reach' 

 rfnd it is probable that the observations which have been 

 secured will be few in number. It is nevertheless evident 

 that the elements are very well determined, a very small 

 Acceleration which is also indicated in previous revolu- 

 tions being sufficient to produce an exact agreement 

 between Prof. Oppolzer's calculations and the result of 

 the first Marseilles observation. Reference was lately 

 rjlade to the Vienna astronomers suspicion of identity of 

 this comet with one of the imperfectly observed comets 

 of 1S08 — that which was discovered by Pons on Feb. 6th 

 and seen again on the 9th. On examining the m.after 

 more closely there appears to be strong reasons to doubt 

 tilis inference, upon which we may enter in a future 

 notice. 



The Zodiacal Light. — Another conspicuous exhibi- 

 tion o\ this phenomenon was observable in the neighbour- 

 hood of London on the evening of February 25. The sky 

 was very vaporous, and the smaller stars usually visible 

 without a telescope were not discerned, but soon after 

 8 P.M. the light was quite a marked object in the heavens ; 

 it did not present the lemon tinge which is commonly the 

 case when the sky is clear, but rather resembled the light 

 of the Milky Way, except that it was of much greater 

 intensity. It could not be traced that evening beyond the 

 constellation Musca. 



New Minor Planet.— Le Verrier's Bulletin of Feb. 

 27 announces the discovery of a new member of the minor 

 planet group by Herr Pahsa at the Observatory of Pcla 

 on the 23rd. Its position at 8h. 42m. local time was in 

 R.A. 9h. 57m. 56s., N.P.D. 76° 14'. The planet is of the 

 twelfth magnitude. 



SCIENCE AT THE NEW PARIS OPERA 



THE New Paris Opera has excited a great deal of 

 attention among all classes, both on the Continent 

 and in England. Every effort has been made to make 

 the building perfect in all respects, and to carry out its 

 construction in harmony with the latest scientific princi- 



ples. Some recent numbers of La Nature contain a 

 series of articles by M. G. Tissandier on the new 

 building, to show in what manner the principles of 

 science have been made to conduce to the wclf.-xrc and 

 comfort of art. A few of the points in these articles we 

 shall bring before our readers, as also some of the 

 illustrations, which have been obhgingly lent us by 

 the proprietors of our sister journal. M. Tissandier 

 deals first with the subject of Warming and Ventilation. 



It is not astonishing that the ventilation of theatres 

 has been effected in a very incomplete fashion, when 

 we consider the difficulties which stand in the way of 

 a complete solution. "A theatre is composed not of a 

 single compartment, like every other place of assembly, 

 but of three vast contiguous compartments : the hall (or 

 auditorium), the corridors, and the stage, all which, at 

 certain times are separated, at others connected by vast 

 openings. To this first difficulty must be added the action 

 of the lustre, which causes a strong current of sonorous 

 waves towards the ceiling, greatly to the detriment of the 

 acoustics and to the equality of temperature in the various 

 parts of the auditorium. The position of the spec- 

 tators in tiers lising one above the other along the 

 walls, and not horizontally, adds a new obstacle to the 

 efficacious renewal of the air. Moreover, the conditions 

 of the problem are constantly changing. Thus, before 

 the entra^nce of the public the heating may have taken 

 place downwards and by the ordinary means ; but, once 

 the public have been admitted and the curtain raised, a 

 considerable mass of air, that of the stage, is put into 

 communication with the body of the theatre. Between 

 the acts this communication ceases; but, on the other hand, 

 there are from 1,000 to 1,500 persons, just so many living 

 stoves, and some hundreds of gas-jets, which heat and 

 gradually vitiate the atmosphere. Hence a change must 

 be introduced in the ventilation ; still another change 

 when the curtain is raised ; and all this to be modified 

 according to the season."* 



At the commencement of the present century the 

 Marquis de Chavannes devised a system, which was tried 

 at Covent Garden Theatre, and which contained the prin- 

 ciple of all the methods since invented. 



The heating of the stage was efifected by steam 

 cylinders, shown at M, in Fig. i. Ventilation took place at 

 N above. The auditorium was heated by the large stove 

 B, which by cylindrical pipes sends warm air under the 

 flooring of the boxes and into the staircases. At R the 

 vitiated air of the boxes met, drawn off by the openings 

 AAA. The vitiated air of the body of the theatre drawn 

 upwards by the lustre, reached O, after having traversed 

 the openings P P. 



In 1828 a commission, composed of Bcrard, Cadet de 

 Gassicourt, Marc, and d'Arcet, was entrusted in France 

 ! with an investigation into the principles of the ventilation 

 i of theatres. Fig. 2 represents the arrangement devised 

 by d'Arcet, who took ad%'antage of the lustre to convey 

 outside the air vitiated by the combustion and by the 

 breath of the audience. The warm air is introduced into 

 the corridors by the openings C C C ; it enters the 

 auditorium by passing under the flooring of the boxes, 

 in the direction of the arrows. The exit of the air takes 

 place at U ; it may be regulated above the lustre by 

 means of the movable traps at T. It is also accomplished 

 at V, Ijy passages which are united in the central 

 chimney. 



These systems had serious drawbacks. An attempt at 

 improvement was made in 1 861, during the construction 

 of the new theatres in the Place du Chatelet. For the 

 purpose of investigating the question a commission vvfas 

 nominated, presided over by M. Dumas, Perpetual Secre- 

 tary of the Academy of Sciences, and having for reporter 

 General Morin, Director of the Conservatoire des Arts 

 et Metiers. After many experiments and many contra- 



• " Traitc "pratique du chauffage et de la ventilation," by V. Ch. Joly. 



