April 24, 1902] 



NATURE 



595 



practical scale is published for the benefit of young engineers 

 and amateurs. The Afodcl Engineer and Amateur Electrician 

 forms the medium for enthusiastic students fond of engineering, 

 and we find in its columns practical working drawings and 

 photographs contributed and explained in a very lucid manner. 

 Under the heading of "Queries and Replies," readers in diffi- 

 culty for information get their wants adequately supplied in a 

 subsequent issue. A good example of this is found on p. 165 

 (April number), where a working general arrangement of a 

 model locomotive is given for a two and a half-inch gauge rail- 

 way and drawn to a scale of half inch to a foot, in the design of 

 which we notice water tubes placed inside and across the fire- 

 box, an idea only intioduced into actual locomotive practice a 

 few months ago. Electricity and petrol motors also form an 

 important part within the columns of the periodical, practical 

 types of dynamos, motors, &c., being thoroughly dealt with. A 

 paper of this description brings within the scope of students a 

 practical application of science to mechanical engineering, 

 enabling them to grasp the fundamental ideas of construction 

 and also to carry them through into a practical working form. 

 In the article by Sir Michael Foster, on the Regina Mar- 

 gherita Observatory, in last week's NATURE (p. 569), the 

 height of the Gnifetti hut, given as 4560 feet, should be 4560 

 metres ; the height in feet is 14,961. 



Seven volumes belonging to the valuable " Scientia " series 

 have been received from the publisher, M. C. Naud, of Paris. Six 

 of the volumes (Nos. 13-18) are in the physical section of the series, 

 and one (No. 12) is in the biological section. Each volume may 

 be described as a short review of knowledge of the subject with 

 which it deals, or a statement of observations and results 

 interpreted in the light of recent scientific thought. The titles and 

 authors of the volumes which have just come to hand are 

 " Cryoscopie," by the late M. F. M. Raoult ; " Franges 

 d'interference," by Prof. J. M. de Lepinay ; "La Geometrie 

 non-euclidienne," by M. P. Barbarin ; " Le Phenomene de Kerr 

 et les Phenomenes electro-optiques," by M. E. Neculcea ; 

 " Theorie de la Lune," by Prof. H. Andoyer ; " Geometro- 

 graphie, ou Art des Constructions geometriques," by M. E. 

 Lemoine ; and ' ' L' Heredite acquise : ses consequences horticoles, 

 agricoles, et medicales," by M. M. J. Constantin. 



The additions to the Zoological Society's Gardens during the 

 past week include a Campbell's Monkey {Cercopithecus 

 campbelli), a Hocheur Monkey {Cercopithecus nictitans) from 

 West Africa, presented by Captain Joseph C. Verey ; a Sooty 

 Mangabey (Cercocebus fuliginosus) from West Africa, a Black- 

 headed Lemur (Lemur brunneus), a Red-fronted Lemur [Lemur 

 rufifrons) from Madagascar, two King Penguins (Aptenodyles 

 pennanti), a Thick-billed Penguin (Eudyptes pachyrhynchus) 

 from the Macquarie Islands, two Common Rheas (Rhea 

 aiitericana) from the Argentine Republic, a Raven (Ccrvus 

 corax) European, two Eupatorian Parrakeets (Palaeornis 

 eupatria), three Indian Rat Snakes (Zamenis mucosa), five 

 Tigrine Frogs (Rana tigrina) from India, deposited. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occurrences in May. 

 May I. ih. Jupiter in conjunction with moon. Jupiter 

 5° 59' S. 

 I. I3h. 12m. to I4h. 7m. Moon occults c' Capricornii 



(mag. 5-2). 

 4. ^h. Venus in conjunction with moon. Venus 



4" 19' s. 



7. Sun partially eclipsed, invisible at Greenwich. 



14. I2h. 9m. Minimum of Algol (fl Persei). 



15. Venus. Illuminated portion of disc = o'5S9, of 



-Mars = 0996. 

 17. 8h. 58m. Minimum of Algol (/3 Persei). 

 NO. 1695, '^OL. 65] 



May 20. Saturn. Outer minor axis of outer ring = 14" 84. 

 20. I3h. l8m. Moon makes a near approach too Libra; 



(mag- 3)- 

 26. 2oh. Saturn in conjunction with moon. Saturn 



5' '^' ^• 

 28. 6h. Mercury at greatest elongation, 23° 3' E. 



28. I2h. Jupiter in conjunction with moon, Jupiter 



5' 57' S. 



29. 4h. Mercury in conjunction with Neptune. Mer- 



cury 2° 52' N. 

 Comet 19020: (Brooks). — The discovery of the first new 

 comet of the present year was made by Mr. Brooks at Geneva 

 on April 15, and the following data are supplied for the position 

 at discovery and various subsequent epochs : — 



April 15 16 o Geneva 347 2 o 62 35 o Brooks. 



„ 16 14 37 Kcenigsberg 34S 55 16 63 53 25 — 



,, 16 15 S-i Copenhagen 349 3 12 63 58 39 Pechiile. 



,, 16 IS 30-2 Bamberg 349 6 54 64 I I Ilartwig. 



,, 16 15 45-6 Lick 350 16 56 64 47 34 Aitken. 



The original announcement of discovery described the comet as 

 being bright, with a tail. A later description by Prof. Hartwig 

 states that the comet is about 8 '5 magnitude, circular in form 

 with a diameter of 3'. There is a central condensation and a 

 tail somewhat less than 30' in length. 



At discovery the new comet was quite close to 3 Pegasi ; it is 

 now moving to the south-east rather rapidly. 



Nebui./e and their Velocities .in the Line of Sight. 

 — Dr. J. Hartmann, of the Potsdam Observatory, gives 

 (Sitzungsberichte der Kon. Preiiss. Akad. dcr Wissenschaften 

 zu Berlin, February 27, 1902) an interesting account of his 

 investigation to determine the velocities in the line of sight of 

 several gaseous nebulse, the spectra of which he has photo- 

 graphed. The work was suggested to him after he had secured 

 a very strong image of the planetary nebula G.C. 439° "i'h ^^^ 

 Potsdam photographic refractor of 80 cm. in the short time of 

 exposure of 15 minutes. In the investigation two spectroscopes 

 were employed, that v/hich he designates apparatus I. consisting 

 of a flint glass prism of 60', a collimator of 530 mm. and a camera 

 of 720 mm. focal lengths ; while apparatus III. has three flint 

 glass prisms of 63°, a collimator of 4S0 mm. and a camera of 

 410 mm. focal lengths. The exposures of the different negatives 

 obtained varied from 90 to 270 minutes, and the comparison 

 spectrum photographed in each case was that of the arc spec- 

 trum of iron ; the nebuke photographed and the spectra of 

 which were examined for movement in the line of sight 

 were G.C. 4390, 4373, and N.G.C. 7027. Dr. Hartmann 

 determined first of all the velocity of the nebula G.C. 4390 

 from the measurements of the hydrogen lines H^ and Hy, and 

 from this value deduced the wave-lengths of the two chief 

 nebula lines. All the values for the velocity as determined 

 from the diff'erent negatives agreed well among themselves, and 

 the deduced mean "values for the wave-lengths of the two 

 nebula lines were 5007-04 and 4959-17. While the former 

 value is practically identical with the wave-length obtained by 

 Prof. Keelerfor the Orion nebula 5007-05 ± 003, the latter is 

 somewhat greater than Keeler's value, namely 4959-02 + 0-04. 

 Dr. Hartmann finds that the discrepancy is easily e.xplained, 

 as Keeler used a spark spectrum of iron for comparison, and 

 the two lines of iron close together at this wave-length behave 

 differently under the two electrical conditions (arc and spark). 

 If it be assumed that Keeler's comparison line was that at wave- 

 length 4957 -78 instead of at 4957-63--and Dr. Hartmann 

 seems to have good reasons for making this assumption — then 

 his own result is brought in complete accord. The paper 

 further gives details of each of the measurements on the 

 different photographic negatives employed, but the following 

 table shows only the mean results obtained, giving Keeler's 

 values for comparison : — 



Nebula Velocity 



Hartmann Keeler 



kni. km. 



G.C. 4390 •■• -io'5 - 97 



G.C. 4373 - -65'8 -647 



N.G.C. 7027 ... + 4'9 -fio-i 



It is interesting to note that Dr. Hartmann finds slightly 



different values of the velocity for the middles in relation to the 



