March 13, 1879] 



NATURE 



437 



phenomena to which it was found that a variation in the 

 condition of gas must gire rise, have been found to 

 exist. 



The results of the investigation lead to certain general 

 conclusions which lie outside the immediate object for 

 which it was undertaken ; the most important ^of these 

 is that gas is not a continuous plenum. 



The experimental results considered by themselves 

 bring to light the dependence of a class of phenomena 

 on the relations between the density of the gas and the 

 •dimensions of the objects, owing to the presence of 

 which the phenomena occur. As long as the density of 

 the gas is inversely proportional to the coarseness of the 

 plates, the transpiration results correspond ; and in the 

 same way, although not so fully investigated, correspond- 

 ing phenomena of impulsion are obtained as long as the 

 density of the gas is inversely proportional to the linear 

 size of the objects exposed to its action ; in fact, the same 

 correspondence is found with all the phenomena in- 

 vestigated. 



We may examine this result in various ways, but in 

 whichever way we look at it, it can have but one meaning. 

 If in a gas we had to do with a continuous plenum, such 

 that any portion must possess the same properties as the 

 whole, we should only find the same properties, however 

 small might be the quantity of gas operated upon. Hence, 

 in the fact that we find properties of a gas depending on 

 the size of the space in which it is inclosed, and on the 

 quantity of gas inclosed in this space, we have proof 

 that gas is not continuous, or, in other words, that gas 

 possesses a dimensional structure. 



In virtue of their depending on this dimensional 

 structure, and having afforded a proof thereof, it is 

 proposed to call the general properties of a gas on which 

 the phenomena of transpiration and impulsion depend, 

 the Dimensional Properties of Gas. 



Although the results of the dimensional properties of 

 gas are so minute that it has required our utmost powers 

 to detect them, it does not follow that the actions which 

 they reveal are of philosophical importance only ; the 

 actions only become considerable within extremely small 

 spaces, but then the work of construction in the animal 

 and vegetable worlds, and the work of destruction in the 

 mineral world, are carried on within such spaces. The 

 varying action of the sun must be to cause alternate 

 inspiration and expiration, promoting continual change 

 of air within the interstices of the soil as well as within 

 the tissue of plants. What may be the effect of such 

 changes we do not know, but the changes go on ; and we 

 may fairly assume that, in the processes of nature, the 

 dimensional properties of gases play no unimportant 

 part. Osborne Reynolds 



OUR ASTRONOMICAL COLUMN 

 The Binary Star a Centauri.— Dr. Doberck, with 

 the aid of measures made during the last few years has 

 calculated elements of a Centauri, which, though given as 

 only provisional, will doubtless approach nearer to the 

 true ones than any previously published. They are as 

 follows : — 



Passage of the peri-astre 



Node 



Angle between node and peri-astre 



Inclination 



Excentricity 



Semi-axis major 



Period of revolution 



... 1875-12 



... 25° 32' 



- 45° 58' 



... 79» 24' 



.•• 0-5332 



... 18" -45 



... 88536 years. 



Comparing this orbit with weighted means derived from 

 Mr. Gill's measures at Ascension in 1877, the following 

 differences are shown : — 



1877-614 

 1877-858 



Position + 2-32 

 ». - o'39 



Distance - 0-23 

 ,. + o-pS 



For 1879-5 the elements give position, I73''4'; distance, 

 3"-47 ; and for i88o"5, position, i85°*2 ; distance, 5"-3o; 

 the smaller star will be due south of the larger one at the 

 beginning of 1880, distant 4"*37. The above value for the 

 semi-axis major, taking the annual parallax of a Centauri, 

 a mean between the values of Maclear and Moesta, indi- 

 cates that the mean distance between the component stars 

 is rather greater that the mean distance of Uranus from 

 the sun. Frequent measures of a Centauri during the 

 next {qw years are much to be desired 



A New Variable Star in Sagittarius. — The fol- 

 lowing case appears a singular one, if the star is not 

 variable to a considerable extent : — On April 28, 1783, 

 D'Agelet observed a star which he estimated of 4*5m., 

 and which is No. 4,627 in Gould's Catalogue. It does 

 not occur in Piazzi or Lalande, nor in Bode, but it is 

 found on Harding's Atlas as 6m. It is wanting in the 

 Uranometries of Argelander and Heis, but the former 

 observed it three times in his Zones. In Z. 218, July 2, 

 1849, it is rated 5m. ; in Z. 225, on July 13, only 7m. ; 

 and in Z. 391, June 30, 185 1, it is 5-6m. The mean posi- 

 tion for 1850 from Argelander's observations is in R.A. 

 I7h. 59ni. 6-575.,N.P.D. 107° 10' 9^-9, orreducingto 1880 

 in R.A. i8h. om. 5ris., N.P.D. 107° 10' 10". It is diffi- 

 cult to account for such an object having escaped the 

 notice of other observers, except upon the supposition of 

 variability ; perhaps, like some other variables, it is only 

 conspicuous for a short time. The star foUows 6 Sagit- 

 tarii 6m. 265., in i'-4 greater N.P.D. It is proper to state 

 here that Mr. J. E. Gore, in his "Southern Stellar 

 Objects," p. 104, has a reference to this star amongst 

 stars possibly variable, but the observations of D'Agelet 

 and Argelander do not appear to have been known to 

 him. 



New Minor Planet. — No. 193 was discovered by M. 

 Coggia at Marseilles on March i, not far from the place 

 of No. 192, detected at Pola by Herr Palisa, in the 

 previous month. 



Intra-Mercurial Bodies.— In a letter addressed to 

 M. Mouchez, communicated to the Academy of Sciences 

 at Paris on March 3, Padre Ferrari, Director of the 

 observatory of the CoUegio Romano, mentions that, 

 having had occasion to institute researches respecting the 

 observation of a rapidly-moving spot upon the sun's disk 

 by De Cuppis on October 2, 1839, ^t the instance of Prof. 

 Oppolzer, he had met with particulars of a similar ob- 

 servation by De V'ico in 1837. Reference is made to this 

 observation in " Memoria intorno ad alcune osservazioni 

 fatte alia Specola del Collegio Romano, 1838," p. 15, but 

 the year only is there mentioned. De Cuppis, a friend 

 and frequently co-operator of De Vico's has, however, 

 preserved the date in the journal L' Album for 1838, July 

 7, where the observation is thus described : " In una 

 osservazione del 12 luglio, 1837 parve al sullodato astro- 

 nomo (De V'ico) del Collegio romano veder rinnovato il 

 fenomeno, in una piccolissima macchia perfettamenta 

 rotonda e senza traccia della cosi detta penombra, la quale 

 nel breve spazio di 6 ore trascorse buona parte del disco 

 solare." 



This observation does not occur in Haase' s Collection, 

 nor is there here more than a reference to the observation 

 of Decuppis, which is thus given in a note by Arago at 

 the sitting of the French Academy on December 16, 

 1839 '• — " M- Decuppis annonce que le 2 Octobre, en con- 

 tinuant des observations qu'il faisait sur les taches du 

 soleil, il a vu une tache noire, parfaitement ronde et k 

 contours nettement terminus, qui s'avangait sur le disque 

 de I'astre d'un mouvement propre rapide, de maniere k 

 ce quelle a du en traverser le diam^tre dans environ six 

 heures. M. Decuppis pense que les apparences qu'il a 

 observ^es ne peuvent s'expliquer qu'en admettant I'exist- 

 ence d'une nouvelle planete." 



There are other observations upon record in January 



