Oct. 4, 1888] 



NA TURE 



559 



part of the earth's orbit there is a stream of meteorites plunging 

 down nearly vertically towards the ecliptic ; the earth in passing 

 through them would receive the greatest number of blows on its 

 exterior atmosphere on the hemisphere above the plane of the 

 ecliptic at the time, while the other hemisphere would be 

 entirely sheltered, so that the direction of the fall would be 

 capable of demonstration by a consideration of the earth's 

 direction and the relation of its surface to the plane of the 

 ecliptic at the time. 



The observations indicate that these bodies are moving 

 towards the plane of the ecliptic, from its northern side, into 

 that part of it through which the earth passes in her annual 

 journey in November ; they, in fact, are moving round the sun 

 in an orbit inclined at a not very large angle — 17" — to the plane 

 of the earth's orbit. 



Similarly, we might observe the August ring rising from one 

 of its nodes, situated in the point of the earth's orbit occupied 

 by our planet on August 10, not at a slight angle like the 

 November ring, but at an angle of 79 or 8o°. 



It is important to make this point quite clear. 



Let us conceive the sun and earth to be half immersed in an 

 infinite ocean which will represent to us the plane of the ecliptic, 

 and let us further for greater simplicity assume that the earth's 

 motion round the sun (in a direction contrary to the hands of 

 a watch) is performed in a circular path with the sun at the 

 centre ; let us, moreover, suppose the earth's path, or orbit, to 

 be marked by buoys, remembering that astronomers define the 

 position of a heavenly body in the plane by stating its longi- 

 tude — that is, its angular distance, reckoning from right to left, 

 from a particular start-point, as seen from the sun ; and its 

 latitude — that is, its angular height above the plane as seen from 

 the same body. 



Now, if it were possible to buoy various points of the earth's 

 orbit in the plane of the ecliptic in the convenient manner 

 before suggested, we should see the meteor-ring of "Leonids" 

 meeting the waves of our hypothetical ocean, at a slight angle 

 (17°), at the point of the earth's orbit occupied by our planet on 

 November 14, the point where they pierce them being called 

 the node. Where the other node lies, where the meteorites 

 cross the plane again, we do not exactly know ; we only know 

 that they do not cross our orbit ; if they did, another star-shower 

 would occur in May. 



Let us inquire into this point a little more clossly. Let us, 

 in imagination, connect the earth and sun by a straight line ; 

 at any moment the direction of the earth's motion will be at 

 right angles to that line (or a tangent to its orbit) ; therefore, as 

 longitudes are reckoned, as we have seen, from right to left, the 

 motion will be directed to a point 90 of longitude behind the 

 sun. The sun's longitude at noon on November 14 was 232°, 

 within a few minutes ; 90 from this gives us 142 , which, as we 

 have seen, is precisely the longitude of the radiant point. This, 

 then, is proof positive enough that in longitude at least the 

 meteoric hail was fairly directed against, and as fairly met by, 

 ihe earth. 



But it will be asked, If the radiant point is situated in lati- 

 tude 8° 30', how comes it that the inclination of the ring is stated 

 lobe 1 7 ? should it not rather be 8° 30'? To this question 

 we may reply by another : How comes it that, when we are 

 hurrying through a shower, we always incline an umbrella at a 

 less angle with the ground than that formed by the falling rain ? 

 The answer is the same in both cases. In the case of the 

 meteorites, if our motion in one direction differs little from 

 heirs, they appear to us to fall at an angle which is also almost 

 precisely half of their real one. 



Similar ancient records relating to star-showers seen in March 

 ind April, and July and August, showed that the earth's longitude 

 vas always the same when thty were observed, if it was raferred 

 o a fixed equinox. The constant longitude for the star-showers 

 mciently recorded to have taken place in March-April corresponds 

 o April 20*id., 1850, and for a like number seen in July-August, 

 \ugust 9 od., 1850. 



Forms and dimensions of the orbit of the August meteors, all 

 >f them very steeply inclined to the ecliptic, were calculated 

 imong the many combined observations and determinations of 

 leights of those meteors made at German Observatories to con- 

 lude their longitudes, in the years following the great November 

 howers of 1832-33, by the German astronomer, Erman. Bui 

 m exact valae of their velocity was still wanting', and from 

 n approximate measure of the velocity of the " Perseids," 

 Attained from observations of a fine meteor of the shower in 



America on August 10, 186 1, Prof. H. A. Newton found 

 elements of the ring, concluding it to be not far from circular in 

 forrr, and nearly perpendicular in its plane to the ecliptic. 



It will be seen that the longitude for the showers re- 

 corded in October-November advances along the ecliptic 

 from a fixed equinox with a uniform motion of 52" per annum. 

 Such a motion as this must be due to planetary perturbation, and 

 hence we are in presence of cosmical phenomena. 



It is to an American astronomer, Prof. Newton, that we owe 

 the first investigation into the constitution of the November 

 ring. 1 He first considered the question whether the ring is 

 of uniform density, and whether it lies merely near our orbit ; 

 the variation in the brilliancy of the showers being caused by 

 the action of the planets and moon on the earth and ring — the 

 greatest perturbation of the earth being 9000 miles each way— 

 sometimes throwing us into the ring, sometimes causing us to 

 pass it without meeting it. He has shown, however, that the 

 ring cannot be of uniform density throughout, but that, on the 

 other hand, in one part of it there is a clustering together of the 

 little bodies of which it is composed — a few stragglers being 

 scattered along the rest of its circuit. 



From other considerations he showed that the meteors 

 revolve round the sun in a direction opposed to the earth's 

 motion, the most probable time of revolution being, according 

 to his first view, 354'62i days, our own being accomplished 

 in 365 '256 days. This is the same as saying that the annual 



motion of the group is I + — — revolutions. Consequently, the 



centre of the group is brought, on this view, into contact with 

 the earth once in every 133 years, but the earth passes very near 

 the centre four times in this interval. 



On this view the orbit of the swarm would be nearly circular. 



With regard to the rings generally, Prof. Newton made out 

 in 1865 -' (1) that all the sporadic shooting-stars cannot belong 

 to a narrow ring which has a diameter approaching in size that of 

 the earth ; and (2) that a large portion of the meteorites, when 

 they meet the earth, are travelling faster than it, or else that the 

 sporadic meteors form a series of radiants at some distance from 

 the ecliptic, and hence come from a series of rings considerably 

 inclined to the plane of the ecliptic. t 



Further, he pointed out that the distribution of the orbits of 

 the meteorites must be one or other of the following : — 



(1) They may form rings passing near the earth's orbit at 

 many points along its circuit (sporadic meteors may be outliers 

 of such a ring). 



(2) They may form a disk in the plane of the ecliptic. 



(3) They may be distributed at random like the orbits of 

 comets. J. Norman Lockyer. 



{To be continued.) 



SCIENTIFIC SERIALS. 



American Journal of Science, September. — Cambrian fossils 

 from Mount Stephens, North- West Territory of Canada, by 

 Charles D. Walcott. The fossils here studied were first dis- 

 covered last year by Otto J. Klotz, and partly described by Dr. 

 C. Romiger. A comparison with specimens from the Middle 

 Cambrian Terrane of Central Nevada shows that the two faunas 

 are identical, and that consequently the Mount Stephens remains 

 should be referred to about the horizon of the upper portion of 

 the Middle Cambrian system. Other discoveries near the 

 Kicking Horse Pass on the Canadian Pacific Railway seem to 

 show that this fauna extends all along the western side of the 

 great Keweenawan continental area from Southern Nevada far 

 into British America. — History of changes in the Mount Loa 

 crateis (continued), by James D. Dana. Here are studied the 

 relations of Kilauea to Mount Loa, arguments being advanced 

 to establish the independent origin of the former, contrary to the 

 author's earlier views on the subject. But his old conclusion is con- 

 firmed that volcanoes are not safety-valves, but are rather indexes 

 of danger, pointing out the parts of the earth's crust that are 

 most subject to earthquakes. A contrast is also drawn between 

 volcanoes of the Mount Loa and Vesuvius types, the discharges 

 of the former being almost exclusively outflows, those of the 

 latter upthrows of cinders combined with lava-streams. — On the 

 formation of deposits of oxides of manganese, by F. P. Dunning- 

 ton. The main object of this paper is to show that manganese 

 sulphate has probably taken a very important part in the 



1 Silli man's Journal, Nos. 111 and 112. 



2 Ibid., vol. x.\x x. 



