June 21, 1883] 



NA TURE 



181 



Geese (Bernicla magellauica £ 9 ), two Ruddy-headed Geese 

 (Btrnida rubidiceps) from the Falkland Islands, presented by 

 Mr. R. C. Packe ; three Common Pheasants (Phasianus colchi- 

 cm $ 9 9 ), British, presented by Mr. H. T. Bowes ; an Indian 

 Python (Python molurus) from India, presented by Mr. G. E. 

 Shute ; a Sykes's Monkey (Cercopithecus albigularis), a Philan- 

 tomba Antelope (Ccphalophus maxwelU 9 ), an Elate Hornbill 

 (Buceros ela/us), a Jardine's Parrot (Pyocephalus gulielmi) from 

 West Africa, an Indian Civet (Viverricula indica), two Wander- 

 ing Tree lies (Dendrocitta vagabunda), from India, a Red-sided 

 Eclectus (Eclectus polychlorus) from New Guinea, five Red-bellied 

 Conures (Cenurus vittatus), a Giant Toad (B11/0 agua) from 

 Brazil, a Horned Lizard (Phrynosoma cornutum) fro n Texas, 

 four Cornish Choughs (Fregilus gratulus), British, purchased ; 

 a Common Rhea ( Rhea americana) from South America, received 

 in exchange ; two Indian Pythons (Python molurus) from India, 

 received on approval ; a Japanese Deer (Cervus sika S ), born in 

 the Gardens. 



OUR ASTRONOMICAL COLUMN 

 The Paris General Catalogue of Stars. — In the last 

 Annual Report issued by Admiral Mouchez we find particulars 

 of the progress of formation of this extensive and important cata- 

 logue. It is intended to contain all the: stars observed at Paris 

 during the forty-five years 1837 to 18S1 inclurive, about 40,000, 

 but it is mainly the result of the revision of Lalande' s stars in the 

 Histoire CHeste ; indeed, for several years past, the meridian in- 

 struments have been almost wholly occupied upon this work, and 

 upwards of 27,000 observations were made daring iSS2, the year 

 to which the Report refers. The entire number of observations 

 upon which the Paris General Catalogue will be founded is about 

 350,000. The positions are referred to three principal epochs ; 

 1845-0 for the years 1837-53, 1S600 for the years 1854-67, and 

 1875'ofor the years 1868-82. A specimen of the form in which 

 it is intended to print the catalogue is appended to the Report. 

 The right ascensions and declinations are given for each prin- 

 cipal epoch, with the number and mean year of the observations. 

 The precessions are reckoned from the yea' 1S75, with the term 

 depending upon the square of the time. The magnitudes and the 

 differences from the positions of the Histoire Celeste are annexed, 

 and where a star has not been o'iserved by Lalande a synonym 

 in some other catalogue is given. In the first column ue have 

 the ordinal number, and in the second the star's number in the 

 reduced catalogue of the Histoire Celeste. It is mentioned in the 

 Report that M. Bossert had undertaken a new deter uination of 

 the places of the stars in that work, making use of the reducti m- 

 tables of the late Doctor von Asten, which are more exact than 

 the tables of Hansen and Nissen, employed for the catalogue 

 published in 1847. M. Bossert has already effected the reduction 

 of 2,300 stars, a voluntary labour which has occupied his leisure 

 hours. It would add to the value of the coluiins showing the 

 differences between the new Paris positions and those of Lalande, 

 if the comparisons could be made with plac-s resulting from the 

 application of von Asten's tables, though it might be necessary 

 to supplement M. Bossert's laudable effjrts. In the last Green- 

 wich Catalogue (1872) the precessions are given to four places of 

 decimals in right ascension (time), and to three places in north 

 polar distance ; the Paris Catalogue gives these quantities with 

 a figure less, which we are inclined to regard as a retrograde 

 step. 



This General Catalogue of the Observatory of Paris is to com- 

 prise two parts, which will be published simultaneously ; the 

 first part forming the catalogue proper, and the second con- 

 taining details of the observations upon which the mean p isitions 

 are founded. Each part will be composed of four volumes ; 

 the first volume of each is intended to appear during the year 

 1884. 



Encke's Comet in the Years 1871-1881.— At the sitting 

 of the Paris Academy of Sciences on June 11, M. Tisserand 

 communicated a note by Dr. Backlund, of the Observatory of 

 Pulkowa, relative to the motion of Encke's Comet in the interval 

 1871-1881. To complete the theory of this comet, it has been 

 necessary to introduce an empirical to the mean motion of the 



form 11' I rzzj.)- The quantity 11', which was found to be nearly 



constant during the period 1819-1868, appears to have under- 



—) 



1200/ 



gone a considerable variation about the latter epoch. Dr. 

 Backlund bases his calculations upon osculating elements for 

 October 27, 1874, which he considered exact enough for his 

 purpose : they give — 



M = i°79"'33355 + A (where 



u' = + 0-051731 



After having carefully reviewed the computation of pertur- 

 bations by Asten, and calculated by two different methods the 

 perturbations during the revolution 1878-1881, Dr. Backlund 

 compared the elements with the observations made in the years 

 1871, 1875, 1878, and 1881. By means of this comparison, he 

 obtains corrections to the elements, and, observing that if 

 there exists a tangential force, which varies the dimensions of 

 the comet's orbit, its effect is not only secular, but also periodic, 

 the periodic terms being always very small, except in the 

 expression for the mean anomaly. This he takes into account, 

 and finally deduces for the corrections of the two quantities 

 above — 



Aju = 4- o" -004745 



Ap = - 0-0059867 



Hence, he says, his investigation proves that the acceleration 

 of the mean motion in the period 1S71— iSSl was less than half 

 the value found by Encke and Asten for the period 1819-1865. 

 Aten's value is + 0-104418. 



CHEMICAL NOTES 



Interesting experiments on the luminosity of gases are de- 

 scribed by W. Siemens in Ann. Phys. Chim. [(ii.) 18, 311], 

 and by E. Wiedemann [ii. 509]. Gases free from solid 

 particles do not become luminous at high temperatures, nor is 

 the luminosity of a flame due to incandescence of the products of 

 combu tion ; if the gases are strongly heated before being burnt, 

 the flame becomes hotter and shorter than it is when the pre- 

 liminary heating is omitted, and the luminous flame is seen to 1 e 

 distinctly separated from the non-luminous products of combus- 

 tion. Siemens seems inclined to regard the chenvcai action 

 which proceeds as the cause of luminosity : if the existence ot 

 an envelope of ether around the molecule^ is assumed, then the 

 reaction of one molecule on another may be regarded as starting 

 vibrations in this envelope, which vibrations give rise to heat 

 ami light rays. Wiedemann especially considers the luminosity 

 of gases under the influence of electric di-charges : he thinks 

 that in the process of charging the electrodes the ethereal enve- 

 1 ipes of some of the gas molecules are distorted ; when dis- 

 charge occurs these envelopes are set into motion, and hence the 

 luminous effects. 



Some time ago Ostwald deduced the relative affinities of 

 various acids in terms of nitric acid taken as 100; by relative 

 affinity is meant the proportion in which two acids divide them- 

 selves between one base, all the reacting substances being in 

 solution. Ostwald has recently investigated this subject by a 

 method different from that formerly employed ; he has studied 

 the rates of action of various ackL on acetamide, and from the 

 results he has deduced the relative velocities of action, and hence 

 the relative affinities. The following ta >le contains the results. 

 In column 11. are placed figures representing the results of his 

 former experiments — 



I. II. 



Hydrochloric acid ... 100 ... 98-0 



Nitric ,, ... 98 ... 100 



Hydrobromic ,, ... 98 ... 95 



Trichloracetic ,, ... 80 ... 80 



Dichloracetic „ ... 40-8 ... 33 



Mon chloracetic ,, ... 13'° ... 7 



Formic „ ... 5' 2 ■•• 3'9 



Lactic „ ... S'2 ... 3'3 



Acetic ,, ... 23 ••• r2 



Sulphuric „ ... 65-4 ... 667 



Oxalic „ ... 22-6 ... — 



Tartaric „ ... 7'5 •■• 5' 2 



Malic ,, ... 4*7 — 29 



Succinic „ .. 2*5 ... I '5 



Citric „ ... 4'° ••• — 



Phosphoric ,, ... 36 ... — 



Arsenic „ ... 3'5 ••• — 



M. Spring continues his researches into the influence of 

 great pressure upon chemical reactions : at a pressure of about 



