May 27, 1880] 



NA TURE 



89 



memoirs he received the gold medal of the Royal Astronomical 

 Society at the hands of Prof. J. C. Adams in 1S52. His re- 

 searches on the profer motion of Sirius also attracted much 

 attention, and many other papers on various astronomical and 

 mathematical subjects weie contributed by him to the Altona 

 journil. His later work at Altona and Kiel chiefly bore upon 

 the determination of differences of longitude; thelast, "Altona 

 G6ttin?en," is to be detailed in a memoir to be published in a 

 few weeks. 



Minor Planets.— Circular No. 136 of the Berliner Astrono- 

 nomischa Jahrbiich nolifies the re-obfervation of Hilda, the 

 most distant of the group of small planets yet known to us, and 

 one wh)ch, with Ismcne No. 190, must at times experience con- 

 siderable perturbations from the action of Jupiter. It has been 

 found at Pola as an object of 13-5 m.,' many degrees from the 

 position assigned in the ephemeris last published, but there 

 seems reason to suspect error of calculation. Thus if the ele- 

 ments of Dr. Kiihtiert in \}a€ Berliner Jahrbttck for 1S80 are 

 employed, though there is a later orbit, the error of the corn- 

 puted place is much less than that shown by the ephemeris in 

 the Berlin Circular, No. 135. The difference of positions 

 appears to indicate that the true period of revolution is even 

 longer than has yet been calculated. 



In the same Circular, No. 136, are new elements of Philomela, 

 attributing to that planet an almost circular orbit, the angle of 

 excentricity being only 0° iS' 36"'8, so that e = 0-005414, which 

 is less than in the case of Venus. 



Medusa, to which has been assigned the shortest period of any 

 of the minor planet group, has apparently pas ed the last oppo- 

 sition without being re-observed, but in addition to much un- 

 certainty as to position, it was likely to fall in a region of the 

 sky which is crowded w ith small star.s, and therefore a search 

 would be attended with much trouble and difficulty. 



Vesla should now be well discernible without the telescope, 

 being in opposition and perihelion this year nearly at the same 

 time, as we have before remarked, magnitude 5 "9. The planet 

 is in perihelion on May 28. 



Comet 1880, II. — The following ephemeris is calculated from 

 elements depending upon observations to May 8 : — 

 R.A. Decl, 



i2h. G.M.T. 



h. m. s. 



Tune I ... 6 29 32 



3 ■•■ 30 41 



5 ••• 3' 49 



7 ■■• 32 57 



9 ■■ 34 S 



II ■■• 35 13 



13 •■■ 36 20 



15 ■■■ 37 27 



17 •■■ 38 33 



19 ••• 39 38 



Log. distance from the 

 Earth. Sun. 



hS: 3S-S ... 0-4108 ... 0-26S3 



50 52-4 



50 7-0 ... 0-4I6S ... 0-2660 



49 22-7 



48 39-4 ... 0-4221 ... 0-2640 



47 57-0: 



47 15-6 ... 0-4267 ... 0-2623 



46 35 'o 



45 55'2 •■■ 0-4307 ... 0-2609 



45 161 



M ... 6 40 43 ... -t-44 37-7 ... 0-4340 ... 0-2599 



PHYSICAL NOTES 

 Prof. Lemstrom, of Helingsfors, has recently described to 

 the Physical Society of St. Petersburg a singular experiment 

 which, unless otherwise explained by some of the circumstances 

 of the experiment not yet publi-hed, must be regarded as a 

 fundamental fact in the physical theory of electricity. He finds 

 that a ring of insulating material when rotated about its axis of 

 symmetry with a high velocity acts like a galvanic circuit, and 

 produces a magnetic "field" in the space within it. Prof. 

 Lemstrom is a disciple of Edlnnd, and regards this experiment 

 as confirmatory of Edlund's theoretical views on the nature of 

 electricity. According to Lemstrom, the ether in the in.-ulator, 

 being dragged along by the ring, produces vortical motion of the 

 ether in the central space, which vortical motion he conceives to 

 be the essential condition of a magnetic field. Arguing from 

 these premises, Lemstrom proceeds to build up an ingenious 

 theory of terrestrial magnetism. The converse operation of 

 rotating an iron bar within a hollow insulating body or insulating 

 medium ought also to produce magneti'in in the bar. The earth 

 being a magnetic body rotating in an insulating medium, ought 

 to be magnetised by rotation about its axis, the axis being the 

 axis also of magnetisation, unless the irregular internal disposition 

 of the magnetic constituents produced an irregular distribution of 

 the magnetism, or unless the distribution w ere affected by the 

 induced magnetism due to movements of electricity in the atmo- 



sphere, as in the aurora, or by the magnetism which would, on 

 Lerastrom's theory, be generated by the revolution of the earth 

 round the sun, and by the motion of the solar system through 

 space. 



M. DuM.-vs, who has been examining the property of certain 

 metals in occluding gases, has found that aluminium may 

 occlude as much as one and a half times its bulk of hydrogen 

 gas, and also shows traces of carbonic acid. The gases were 

 given up when the metal was heated to redness under exhau-tion. 

 Magnesium behaves similarly. Were these metals distilled in 

 vacuo they could probably be obtained pure. It is possible that 

 these observations may throw some light on the anomalous 

 behaviour of aluminium when used as an electrode in the 

 voltameter. 



The cone of rays entering the eye from a peripheric point 

 is never again united to one point, but it must present some- 

 where a minimum of cross section. The geometrical place 

 of this minimum of cross section Herr Matthiessen {Arch. f. 

 Ofhthalm. (4) 25, 1879) designates the "theoretic retina." He 

 finds that it is a spherical surface, the middle point of which 

 coincides with the middle point of the corneal ellipsoid. To a 

 distance of 75° from the fovea centralis the theoretical retina 

 corresponds very exactly to the actual (according to the deter- 

 minations of Arlt and Helmholtz). At greater distances the 

 retina is formed hypermetropically, and so is within the 

 " theoretic retina." 



The influence of magnetisation on the tenacity of iron has 

 been lately studied by Signer Piazzoli (of the Catanian Academy 

 of Sciences). Iron wires were hung between two hooks and 

 ruptured by pouring water into a vessel suspended from them. 

 They were about 350 mm. long, and were inclosed in a spiral 

 with four windings one over another, which were either all 

 traversed by a current in one direction, or two by a current in 

 one direction, and two by an equal opposite current, so that in 

 both cases the wires were equally strongly heated by the spiral, 

 but in one case they were magnetised, in the other not. The 

 weights required to break wires annealed in charcoal (weight of 

 one metre, G = 0-299) were, during magnetisation, P = 1260- 

 1306 ; without magnetisation, P' = 1213-1270. In the case 

 of wires annealed in carbonic oxide (where G — 0-46 g.), P = 

 1732-4 - 1742-7; P' = 1703-62 - 1719-S7. In the case of 

 wires annealed in hydrogen P = 1289-5 — 1310-1 ; P' = 1263 - 

 1299-7. In each separate series, accordingly, the difference 

 P - P' was frequently less than the difference between the 

 highest and lowest weights required for rupture of apparently 

 identical wires ; still, the mean values in each of the (14) series, 

 were from about I to 3 per cent, greater for the magnetised than 

 for the unmagnetised wires, showing that the tenacity of iron 

 increases on magnetisation. This, it is remarked, need notbe 

 attributed to a change of cohesion of the iron, but may be due to 

 ordinary magnetic attraction of the successive parts of the wu-es. 

 In eleven out of fourteen cases the relative elongation of the 

 magnetised wires at rupture was gi-eater than that of the un- 

 magnetised, in three cases less. 



In a recent note to the Vienna Academy, Prof. Ludwig gives 

 the results of the first of a series of observations on the decom- 

 position of organic compounds by zinc powder. This relates to 

 alcohols, and it is stated that in distillation of these over zinc 

 powder heated to 300 - 350° C, the higher ones— from ethylic 

 alcohol upwards — are split up into the corresponding olefine and 

 hydrogen. Under the same conditions methylic alcohol is 

 decomiosed simply (if the small quantities of marsh gas be 

 neglected) into carbonic oxide and hydrogen. The similar 

 decomposition of ethylic alcohol into marsh-gas, carbonic oxide 

 and hydrogen, only occurs at a considerably higher temperature 

 —with dark red glow. On the ground of these decompositions, 

 which indicate that the combination of the carbon and the 

 oxygen must be a very strong one, it is supposed that the de- 

 composition of the higher alcohols is no simple reduction to the 

 saturated hydrocarbons, from which, then, by separation of 

 hydrogen, the olefines might arise, but that in the first phase of 

 the process the alcohol is split up into the olefine and water, and 

 that the hydrogen concentrated in the gases is due to a reduction 

 of the generated steam by the zmc pow der. 



Prof. Righi has recently described to the Bologna Academy 

 an arrangement of Holtz's electric machine, in which the whole 

 machine except the handle and the electrodes is inclosed, along 

 with a small f-iction machine for excitation, in a glass case tightly 



