44 



NATURE 



{May 10, 1883 



The additions to the Zoological Society's Gardens during the 

 past week include a Macaque Monkey (Macaws cynomolgus) 

 from India, presented by Mrs. Florence A. Hill ; a Common 

 Rhea [Rhea amtricana) from Uruguay, presented by Mr. F. R. S. 

 Balfour ; a Common Kestrel ( Tinminailiis alaudarius), British, 

 presented by Mr A. Lidbury ; a Wood Owl (Syrnium aluco), 

 British, presented by Mrs. W. Duncan ; two Horned Lizards 

 (Phrynosoma cornutum) from Texas, presented by Mr. John G. 

 Witte ; two Marbled Newts ( Triton marmorata) from France, 

 presented by Mr. G. H. King ; two Viverrine Cats (Felts viver- 

 rina), an Indian Otter (Ultra nair), an Indian Darter (Flatus 

 melanogaster), a Hamilton's Terrapin (Clemmys hamiltoni), three 

 Indian Gazelles (Gazella bennettf) from India, deposited ; two 

 Natterjack Toads (Bufo calamita), four Marbled Newts ( Triton 

 marmorata), four Short-nosed Sea Horses (Hippocampus anti- 

 quorum), from France, purchased ; a Black Wolf (Cam's niger) 

 from India, received in exchange; an Eland (Oreas canna 9), 

 born in the Gardens. 



OUR ASTRONOMICAL COLUMN 

 D'Arrest's Comet. — Although M. Leveau's elements ol 

 this comet for the approaching return to perihelion were com- 

 municated to the Academy of Sciences of Paris on January 

 22, they were unaccompanied by predicted places, and it would 

 appear that the ephemeris has had only a very limited circulation, 

 being confined, if we are rightly informed, to those observers 

 who are in possession of the larger instruments. Hence com- 

 paratively few persons may have become acquainted with the 

 circumstances under which this return of the comet to perihelion 

 takes place, and it may not be without interest if we briefly 

 examine the conditions as compared with those of former 

 appearances. 



Assuming as usual the intensity of the comet's light (1) to be 

 represented by the reciprocal of the product of the squares of 

 the distances from the earth and sun, we find the following 

 values : — 



I. 



1851. Last observation at Berlin, Oct. 6 0590 



1858. Last observation tt the Cape, Jan. 18 ... 0-151 

 1870. Last observation at Athens, I>ec. 20 ... 0.154 

 1877. Last observation at Athens, Sept. 10 ... 0-127 



The greatest distance from the earth at any of these dates was 

 I 93 on January 18, 1858. > 



M. Leveau's elements for the approaching return apply to 

 1883, June i2 - o M.T. at Paris ; neglecting, of course, the small 

 effect of perturbation in the interval, the perihelion passage is 

 found to take place 18S4, January 13*5765 M.T. at Greenwich. 

 The coordinate constants for apparent eqiinox of 18S3, May 1, 

 are : — „ , 



x = r. [999502] sin (v + 50 137). 



y - r . [9-99308] sin (v + 321 48-0). 



<s — r. [9-36631] sin (v + 280 38-1). 



Hence we have the following approximate positions and dis- 

 tances of the comet, with the corresponding values of the 

 theoretical intensity of light, taking dates near the time of new 

 moon : — 



i2h. R.A. Decl. Distance from . 



G.M.T. h. m. Karth. Sun. 



June 6 ... 13 96 ... +12 48 ... 2*037 •■• 2615 ... 0-035 

 July 4 ... 13 137 ... +10 12 ... 2-185 ... 2-415 ... 0-036 

 Aug. 2 ... 13 370 ... + 5 42 ... 2-321 ... 2-204 •■• 0-038 

 Nov. 29 ... 17 58-6 ... -16 55 ... 2281 ... 1-427 ... 0-094 

 Dec. 29 ... 19 457 ... -18 8 ... 2-244 •■■ r 338 ■■• o'lii 

 Whence it will be seen that even when most favourably circum- 

 stanced, towards the end of the year, the intensity of light will 

 be less than the lowest value at which the comet has hitherto 

 been observed, viz. 0-127. On November 29 the comet sets 

 about 2h. 8m. after the sun. It was missed at the return in 

 1864, and the chances of observation at its present visit are by 

 no means encouraging. 



Mr. Common informs us that he has made a thorough search 

 or the comet with his large reflector, but without success up to 

 May 7. He remarks that the number of faint nebulae about its 

 t rack is surprising. 



The orbit of this comet almost intersects that of the lost 

 comet of De Vico, 1844; in heliocentric longitude 339°'37', 

 with the elements of 1S51, tire distance between the orbits was 

 only 0-0055 or 507,000 miles. 



Tempel's Comet, 1S73 II. — The corrected elements of this 

 body by M. Schulhof, from observations at its last appearance 

 in 1878, indicate that, neglecting perturbations, it may be again 

 in perihelion about November 20. The positions calculated 

 on this assumption show that the comet will be very unfavour- 

 ably placed for observation, and it may escape detection at this 

 return. 



RULES AND REGULATIONS FOR 7 HE PRE- 

 VENTION OF FIRE RISKS ARISING FROM 

 ELECTRIC LIGHTING* 

 '"PHESE rules and regulations are drawn up for the reduction 

 •*■ to a minimum, in the case of electric lighting, of those 

 risks of fire which are inherent in every system of artificial illu- 

 mination, and also for the guidance and instruction of those v. ho 

 have, or who contemplate having, electric lighting apparatus 

 installed on their premises. 



The difficulties that beset the electrical engineer are chiefly 

 internal and invisible, and they can only be effectually guarded 

 against by "testing," or probing with electric currents. They 

 depend chiefly on leakage, undue resistance in the conductor, 

 and bad joints, which lead to waste of energy and the dangerous 

 production of heat. These defects can only be detected by mea- 

 suring, by means of special apparatus, the currents that are 

 either ordinarily or for the purpose of testing, passed through 

 the circuit. Should wires become perceptibly warmed by the 

 ordinary current, it is an indication that they are too small for 

 the work they have to do, and that they should be replaced by 

 larger wires. Bare or exposed conductors should always be 

 within visual inspection and as far out of reach as possible, since 

 the accidental falling on to, or the thoughtless placing of other 

 conducting bodies upon such conductors, would lead to "short 

 circuiting," and the consequent sudden generation of heat due to 

 an increased current in conductors not adapted to carry it with 

 safety. 



The necessity cannot be too strongly urged for guarding 

 against the presence of moisture and the use of "earth" as 

 part of the circuit. Moisture leads to loss of current and to 

 the destruction of the conductor by electrolytic corrosion, and 

 trie injudicious use of " earth " as a part of the circuit tends to 

 magnify every other source of difficulty and danger. 



The chief dangers of every new application of electricity arise 

 from ignorance and inexperience on the part of those who supply 

 and fit up the requisite plant. 



The greatest element of safety is therefore the employment of 

 skilled and experienced electricians to supervise the work. 



I. The Dynamo Machine 



1. The dynamo machine should be fixed in a dry place. 



2. It should not be exposed to dust or flyings. 



3. It should be kept perfectly clean and its bearings well 

 oiled. 



4. The insulation of its coils and conductors should be practi- 

 cally perfect. 



5. All conductors in the dynamo room should be firmly sup- 

 ported, well insulated, conveniently arranged for inspection, and 

 marked or numbered. 



II. The Wires 



6. livery switch or commutator used for turning the current 

 on or off should be constructed so that when it is moved and left 

 it cannot permit of a permanent arc or of heating. 



7 Every part of the circuit should be so determined, that the 

 gauge of wire to be used is properly proportioned to the currents 

 it will have to carry, and all junctions with a smaller conductor 

 should be fitted with a suitable safety fuse or protector, so that 



1 Recommended by the Council of the Society of Telegraph Engineers 

 and of Electricians in accordance with the Report of the Committee ap- 

 pointed by them on May n. 1882. to consider the subject. Members of the 

 Committee:— Pr.f. W. G. Adams, F.R.S , Sir Charles T Bright, T. Russell 

 Crampton. R. E. Crompton, W. Crookes. F. K.S., Warren De La Rue, 

 D.C I... F.K.S., Pr,,f. G C. Foster, F.R.S., Edward Graves, J. E. H. 

 Gordm, Dr. J. Hopkinson, F.R.S.. Prof. D. E. Hughes. F.R.S., W. H. 

 Preece. F.R.S., Alexander Siemens, C. E. Spagnjletti, James N. Shool- 

 bred, Augustus Stroh, Sir William Thomson, F.R.S., Lieut.-Col. C E. 

 Webber, R. E. 



