256 



NA TURK 



\_July io, ii 



occur when the N. P.D. of the sun was neither great nor small, 

 but midway between the two extremes. These facts will be 

 made clearer by the accompanying woodcuts, in which the globes 

 are shown in four different positions. Fig. 45 represents cases 1 

 and 3, and Fig. 46 cases 2 and 4. In Figs 47 and 4S these facts 

 are shown in different ways : Fig. 47 represents the aspect of the 

 earth as seen from the sun at the summer solstice, when it will be 

 seen that England is seen to lie near to the centre of the hemisphere ; 

 while in Fig. 48, representing the conditions at the winter solstice, 

 England is so near the edge that it cannot be properly repre- 

 sented. This experiment then will enable us to go further, and 

 to say that the plane of the earth's equator, and therefore of the 

 earth's spin, is not parallel to the plane of the ecliptic, but is 

 inclined to it at an angle represented by the difference between 

 90° and 66°, or go" and 113" ; that is to say, the angle between 

 these two planes, that of the earth's rotation and that of its 

 revolution, is something like 23 . 



In the non-coincidence of these two planes we have one of 

 the most fundamental p lints in astronomy, for the reason that 

 what Greenwich is to earth measurement the point of intersec- 

 tion of these two planes is to heaven measurement. The result 

 of this inclination of these two planes is that at one particular 

 point in its course round the sun the equatorial plane of the 

 earth seems to plunge below the plane of the ecliptic, whilst at 

 another and an opposite point it seems to come up from below 

 that plane. 



These two "points are known as the nodes of the orbit, the 



at London). 



ascending nude at that point where the earth comes up from 

 below, the descending node when it is plunging down from 

 above. It will be remembered that when the question of terres- 

 trial longitude was occupying our attention it was pointed out 

 that it might begin anywhere : we begin at Greenwich, the French 

 prefer Paris, the Americans Washington, and so on. With 

 regard to celestial longitude, although it also might begin any- 

 where, yet there is a general agreement among astronomers that 

 the right ascension of stars shall be counted from this ascending 

 node, or, as it is otherwise called, the first point of Aries, where 

 we get the intersection of the earth's plane of rotation with the 

 ecliptic plane of revolution. That is the start-point not only of 

 right ascension for the stars, but of celestial longitude, because it 

 is necessary that we should have a means of determining the 

 positions of stars, not only with reference to the plane of the 

 earth's rotation, but with reference to the plane of the ecliptic 

 itself, and the numl ler of degrees which a heavenly body is observed 

 above or. below that plane (such degrees being called degrees of 

 celestial latitude) require to be known in order to determine 

 absolutely tin- position of any star. With the transit instrument 

 and the sidereal clock the precise angle of intersection of these 

 planes is determined, but ii is necessary to know also the precise 

 point in the orbit at which the intersection takes place, before 

 we can use either our transit instrument or our clock for the 

 determination of the precise position of a heavenly body. And 



now that so much has been said, we can go further with regard 

 to our sidereal clock, and say that it shows oh. om. os. when 

 the first point of Aries is exactly on the central wire of the transit 

 instrument, and that it will come back to that time, oh. om. os., 

 after an interval of twenty-four hours. In that way, by dis- 

 cussing the point of the intersection of the planes, we come to 

 the conclusion not only that the earth's axis is inclined 234° to 

 the ecliptic plane, but that we have at that point the most "con- 

 venient starting point both for the right ascension of stars as 

 determined by a sidereal clock, and the longitude of stars, if we 

 choose to define their positions with reference to the ecliptic plane, 

 instead of with reference to the plane of the earth's rotation. 

 It is curious how in dealing with these matters we find that 

 phenomena apparently the most diverse are really bound up in 

 a most intimate connection with each other. In further con- 

 sidering the subject it will be seen that not only do we get these 

 precious start-points from these considerations, but that they bring 

 before us questions of the greatest interest and value to all earth- 

 dwellers, questions that enable us accurately to study not only 

 time as applied to the dealing out of our days and nights, as 

 applied to those changes which take place during the year, as 

 applied to those changes which effect the years themselves, but 

 as applied to those yet greater changes which have probably 

 been going on in this planet of ours for very many millions of 

 years. j. Norman Lockyer 



( To be continueJ. ) 



ZOOLOGICAL NOMENCLA TURE 

 /"\N Tuesday last week a meeting was held in the Lecture Room 

 -' of the Natural History Museum, where a number of leading 

 British zoologists assembled to meet Dr. Elliott Coues, who is 

 now on a visit to this country, and to hear from him an exposition 

 of tin- views advocated by himself and the leading American 

 zoologists, with regard to the adoption of Trinomial Nomen- 

 clature. 



Among those present were representatives of many branches 

 of science, and we noticed the following British naturalists ; — 

 Lord Walsingham, Prof. Flower, F.R.S., Dr. GUnther, F.R.S., 

 P. L. Sclater, F.R.S., Dr. H. B. Woodward, F.R.S., Prof, 

 Traquair, F.R.S., W. T. Blanford, F.R.S., Henry Seebohm, 

 F.L.S., Howard Saunders, F.L.S., Prof. F. Jeffrey Bell, J. E. 

 Harting, F.L.S., G. A. Boulenger, H. T. Wharton, F.L.S., 

 S. O. Ridley, F.L.S., W. F. Kirby, Sec. Ent. Soc, Herbert 

 Druce, F.L.S., W. R. Ogilvie Grant, and R. Bowdler Sharpe, 

 F.L.S. 



The chair was taken at 3 p.m. by Prof. Flower, 'F. R.S., the 

 Director of the Natural History Museum, who briefly opened 

 the proceedings by reading a letter from Prof. Huxley, P.R.S., 

 expressing his great regret at not being able to be present, 

 being prevented by pressure of official business. 



The Chairman said : — The subject we have met to discuss is 

 one of extreme importance as well as difficulty to zoologists, for 

 though in so many respects the name attached to any natural 

 object is the most trivial and artificial of any of its attri- 

 butes, and may hardly be thought worthy of scientific considera- 

 tion, laxity in the use of names causes endless perplexities and 

 hindrances to the progress of knowledge. I must confess that I 

 feel some sympathy with the young lady, lately quoted in a speech 

 by Sir John Lubbock at the University of London as an instance 

 of hopeless stupidity, who, after listening to a lecture on astro- 

 nomy, said she had no difficulty in understanding how the dis- 

 tances, motions, and even chemical composition of the stars were 

 discovered, but what puzzled her was how their names were 

 found out. Now, I have often had little difficulty in making out 

 the characters and structure of an animal, and even the functions 

 of some of its organs, but when I have to decide by what name 

 to call it, I am often landed in a sea of perplexity. Yet those 

 of us who work in museums are constantly engaged in cata- 

 loguing and labelling, and we are supposed to be able at once to 

 give the correct name to every creature in the collection. I hope 

 that this discussion will help to clear up our ideas upon the sub- 

 ject. With the impartiality due from the chair, I shall not give any 

 opinion upon the merits of the rival schemes to be proposed, at 

 all events not until after hearing the arguments to be brought 

 forward for or against them, and I cannot say that I am very 

 sanguine of being able to do so then. I now call upon Mr. R. 

 Bowdler Sharpe to read a paper " On the expediency, or other- 

 wise, of adopting Trinomial Nomenclature in Zoology." 



