Sept. 20, 1877] 



NA TURE 



441 



speaVer, yet that physical E., according to its definition, is not 

 capable of having such epithets applied to if, except in senses 

 which are not intended by those doctors. Active E. would not 

 be E. or "the fmver of performing work," it would be rather 

 the performing of that work. " Active E." being thus incorrect, 

 its above antithetic?, or approximate antithetics, are incongruous 

 expressions, or else have meanings different from what is in- 

 fended. If " reposing, ' "dormant," " quiescent " E. have any 

 meaning, it is that of " unaz'ailable E." If " quiet" and "tran- 

 quil " E. have any meaning, it is that of E. spending itself 

 slowly and equably. Poor P. thinks that the expression, " pas- 

 sive E. ," would sound very like a bull, whether used in a tap- 

 room or in a lecture theatre. He dares not entertain the 

 suspicion that these expressions had their origin in a momentary, 

 latent, unconscious contusion between kinetic E. and action in 

 the minds of the writers ; but he knows that they are eminently 

 calculated to cause a chronic intentional muddling of them both 

 together in his own brainpan. 



Dublin {7'o be con/inutd.) X. 



On the Supposed Action of Light on Combustion 

 The results obtained in the experiments mentioned by M. C. 

 Tomlinson are to be attributed to the elevation of temperature 

 of the candles exposed to solar light and /teat. 



The influence of light on combustion has been mistaken for 

 the action of heat, which, in this instance, seems to have accele- 

 rated combustion, and in other instances retards it by increasing 

 the heat of the air and diminishing the draft. That is why 

 the sun shining over chimney-pots is said to cause smoke ; it 

 diminishes the ascensional speed of the air through the pipe. 

 Jersey, September 2 G. Savary 



[On referring to Mr. Tomlinson's paper we find that out of 

 four trials, with a number of candles to each, there was a greater 

 consumption of material in the first and fourth trials in the light 

 than in the dark ; and in the second and third trials the con- 

 sumption was greater in the dark than in the light ; but in any 

 ca.se the difference was so small, amounting only to from two to 

 seven grains per hour, that it may fairly be referred to accidental 

 circumstances, such as differences in temperature, in currents of 

 air, and in the composition and matter of the candles. Some of 

 the trials were made in the diffused light of day, and in all the 

 trials the differences in temperature between the daik and the 

 light spaces were but small. — Ed.] 



OUR ASTRONOMICAL COLUMN 

 The Satellites of Mars.— The following ephemeris 

 of the outer satellite is deduced from the elements given 

 in this column last week, except that the daily motion is 

 corrected to 285° 5''i47 by observations to Sept. 16 : — 



At 8h. om. At loh. om. G.M.T. 



Pos. Dist. Pos. Dist. 



Sept. 24 .. 247 ... 75 ... 23'7 ... 61 



. ,, 25 ... 2S0 ... 49 ... 276 ... 68 



„ 26 ... 52 ... 54 ... 26 .. 34 



„ 27 ... 83 ... 70 ... 75 ... 77 



,, 28 ... 192 ... 29 ... 129 ... 31 



,, 29 ... 252 ... 76 ... 243 ... 68 



,, 30 ... 297 ... 35 ... 274 ... 55 



Oct. I ... 60 ... 63 44 ... 44 



„ 2 ... 90 ... 59 ... 80 ... 71 



„ :3 - 217 •■• 38 ■■■ 167 ■■■ 25 



,, 4 •■• 257 ... 72 ... 249 ... 70 



,, 5 ... 328 ... 26 ... 286 ... 41 



For the inner satellite the following elements may be 



taken as representing closely the Washington measures, 



August 17-20 : — 



Passage of Ascending Node, August I7'89788 G.M.T. 



Longitude of node 82 48 



Inclination of orbit 25 24 



Period of revolution o'3i84i days. 



Log. radius of orbit at mean distance of ) „, 



Mars from the sun j o-92bt) 



They show the following differences of the calculated 



angles from those observed : — 



Aug. 17 

 „ 18 



Aug. ig 



+ I 9 



-f 0-1 



The outer satellite has been observed on several nights 

 by A. A. Common, Esq., of Ealing, with an 18-inch silver- 

 on-glass reflector. On the ijth'and l6th inst. excellent 

 measures were made with this instrument, by means of 

 which the period of revolution was corrected before calcu- 

 lating the above ephemeris. Mr. Common has stated to 

 the writer that the satellite is ruddy, even more deeply- 

 coloured than the body of the planet. It has also been 

 observed on several occasions by M. M. Henry at the 

 Observatory of Paris. 



Employing Kaiser's value of the mean diameter of Mars 

 at distance unity (9"-472) it results that the inner satellite 

 is distant from the centre of the primary 2730 and the 

 outer one 6'846 semi-diameters. As seen from the inner 

 satellite the globe of Mars will subtend an angle of 40"^, 

 and as seen from the outer satellite, one of about i5°. 

 The orbital motions per minute are respectively seventy- 

 nine miles and fifty miles. Our own moon has a mean 

 orbital velocity of thirty-eight miles per minute. 



The Satellite of Neptune.— The subjoined ephe- 

 meris is derived from Prof. Newcomb's tables : — 

 At I3h. Greenwich M.T. 

 Pos. Dist. Pos. Dist. 



Oct. 9 ... 2's ... 13-6 



„ 10 . loi ... 63 



162 



130 



7-5 

 i6-5 



12-3 



7-5 

 167 

 The motion of this satellite is 7-clro(rrade both with 

 reference to the equator and to the ecliptic, and thus it 

 presents the most decided case of retrograde motion in 

 the planetary system ; the motion of the satellites of 

 Uranus, though retrograde upon the ecliptic, is direct 

 upon the equator. For 1S77 we have for the satellite of 

 Neptune, from Prof. Newcomb's investigation — 



For Equator. For Ecliptic. 



Node 1S3 3 ... 184 33 



Inclination 121 42 ... 145 13 



Adopting the mean of Mr. Lassell's and Mr. Marth's 

 measures of the diameter of Neptune, taken at Malta in 

 1864-65, as the most reliable value hitherto published, we 

 find that Prof. Newcomb's mean angular distance of the 

 satellite from Neptune corresponds to a true distance of 

 I4'552 semi-diameters of the primary (or about 219,000 

 miles), which will therefore present an angular diameter 

 of rather less than 8° as viewed from the satellite. The 

 period of revolution being 5 '8769 days, the mean orbital 

 velocity of the satellite is 162 miles per minute. 



The Binary a Centauri. — Mr. Gill has found time to 

 measure this fine star with Lord Lindsay's heliometer at 

 his present station. Mars Bay, Ascension, on four nights 

 between July 22 and August 5. The distance of the 

 components was then little over two seconds, the bright 

 star preceding. The measures are evidently difficult from 

 the magnitude and closeness of the stars, the separate 

 night's results differing by more than 10° ; but Mr. Gill 

 will doubtless establish an important epoch, and we may 

 hope at the end of the year to have something like 

 reliable elements of this the mo^t interesting of all the 

 revolving double stars. 



Meteoric Astronomy.— The second pait of the 

 publications of the Royal Observatory at Munster has 

 appeared, and is entitled, " Resultate der in den 43 Jahren 

 1833-1875 angestellten Sternschnuppen-Beobachtungen, 

 von Dr. Eduard Heis." It was close upon completion at 

 the time of Dr. Heis's decease on June 30, the revision of 

 the final sheets having been undertaken by one of his 

 pupils. The work contains the times of occurrence and 



