214 



KNOWLEDGE ♦ 



[Sept. 12, 1884. 



the vertical distance between ahall be not Igbb than C ft. 

 and not more than 10 ft. ; and so that the horizontal dis- 

 tance between them measured in a line with the keel of 

 the vessel shall be not less than 5 ft. and not more than 

 10 ft. The lowest of these two lights shall be the more 

 forward, and both of them shall be of such a character, 

 and contained in lanterns of such construction, as to show 

 all round the horizon, on a dark night with a clear atmo- 

 sphere, for a distance of not leas than three miles. 



(c) A vessel employed in line fishing with her Unes out shall 



carry the same lights as a vessel when engaged in fishing 

 vpith drift nets. 



(d) If a vessel w^hen fishing becomes stationary in consequence 



of her gear getting fast to a rock or other obstruction, 

 she shall show the light and make the fog signal for a 

 vessel at anchor. 



(e) Fishing vessels and open boats may at any time use a flare- 



up in addition to the lights which they are by this Article 

 required to carry and show. All flare-up lights exhibited 

 by a vessel when trawling, dredging, or fishing with any 

 kind of drag net, shall be shown at the after part of the 

 vessel, excepting that, if the vessel is hanging by the 

 stern to iier trawl, dredge, or drag net, they shall be 

 exhibited from the bow. 



(/) Every fishing vessel and every open boat when at anchor 

 between sunset and sunrise shall exhibit a white light 

 visible all round the horizon at a distance of at least one 

 mile. 



(g) In fog, mist, or falling snow, a drift net vessel attached to 

 her nets, and a vessel when trawling, dredging, or fishing 

 with any kind of drag net, and a vessel employed in line 

 fishing with her lines out, shall, at intervals of not more 

 than two minutes, make a blast with her fog horn and ring 

 her bell alternately. 



A ship whyih is being overtaken by another shall show 

 from her stern to such last-mentioned ship a white light or 

 a flare-up light. 



An " Officer of the Watch," writing to the Times, says : — 



" In the June number of the Nautical Magazine, a letter ap- 

 peared pointing out the necessity of screening all lights about the 

 decks of ships at sea, except those which are required by the Board 

 of Trade for the prevention of collision, and stating that the Board 

 of Trade surveyors would do well to see that the proper means 

 were at hand for so doing, as the chances of collision would be 

 thereby diminished. On my last homeward passage, in the Bay of 

 Biscay, a large outward-bound steamer was passed between 8 and 

 10 o'clock one night on our starboard side, and so great was the 

 glare from the lights in her deck saloon (which I took to be lighted 

 by electricity) that her green light was completely outshone, and 

 could not be seen, though well within the range of visibility. 1 

 should venture to say that, from the size and speed of the ship, she 

 belonged to one of the finest lines of steamers running, and it 

 seems to me rather strange that those in authority in the managing 

 departments of large steamship companies are not alive to what 

 might be a very fruitful source of collision. Had dense smoke 

 obscured the masthead light of this steamer, the direction in which 

 she was travelling would have been left to conjecture." 



THE EARTH'S SHAPE AND MOTIONS. 



By Richard A, Proctor. 

 CHAPTER IV. (conHnued from page 196.) 



OF all parts of the earth's surface the Equator is that 

 where the evidences of the real nature of the earth's 

 relations to surrounding space are most convincing. I 

 think it probable that to many of my readers an account 

 of the nature of the diurnal rotation of the heavens, as 

 witnessed from the Equator, may be at once new and 

 interesting. 



The north pole, as I have mentioned, has sunk to the 

 horizon when our voyager reaches the equator. Another 

 pole, whose existence had hitherto only been indicated, is 

 now raised from beneath the southern horizon, and lies 

 directly opposite the northern pole. Thus a circle carried 



from the east point of the horizon through the point ver- 

 tically overhead, and so down to the western horizon, 

 divides the visible heavens into a northern and a southern 

 half, the motions within one half corresponding exactly to 

 the motions within the other. 



Fig. 1. 



In Fig. 1, let represent the station of the observer, 

 E, S, W, and N, the east, south, west, and north points of 

 his horizon, Z the point overhead, then E Z W represents 

 the course of a star which rises in the east, and the other 

 curves represent the course of stars rising towards the 

 south and north of east. Every star rises straight up 

 from the horizon, and sets equally square to it. Every 

 star, too, is above the horizon, while describing exactly 

 half of its visible course. Further, as the sun is also 

 visible above the horizon while traversing one-half 

 of its diurnal circle — in other words, as night and day 

 are equal — every star which is visible when the sun 

 sets has passed to the west and set there before the sun 

 rises again ; and every star invisible when the sun set, 

 makes its appearance above the eastern horizon before the 

 sun rises. In other words, all the stars upon the sphere 

 of the lieavens become visible in the course of a single clear 

 night at any place upon the Equator* So that the observer 

 can no longer feel any doubt that the earth is limited in 

 all directions beneath the horizon. 



Let us consider, then, what our observer has already 

 learned respecting the earth's figure. We shall see that 

 he has obtained enough information to suggest very definite 

 views about the dimensions of the globe on which he has 

 travelled. 



His first station was at A (Fig. 2). He travelled north- 

 wards to B, and afterwards southwards to C, establishing 

 by the most indisputable evidence the fact that the arc 

 B C is circular, and that the distance of any point upon it 

 from O, the centre of the circle to which the arc belongs, is 



* After carefully considering the appearances thus presented to 

 the observer situated on the Equator, and recognising the con- 

 vincing evidence these appearances give respecting the trne 

 character of the diurnal rotation, the reader can conceive the 

 indignation with which many gallant naval officers who had often 

 crossed the Equator heard one of the paradoxists lecture at 

 Plymouth to the effect that there is only eue pole of the heavens 

 around which all the stars circulate in places parallel to the plane 

 surface of the esirth. The lecturer, who was as well aware as they 

 were of the absurdity of his views, succeeded in convincing the 

 simpler among his audience, by asserting that in a particular 

 number of the Times which he quoted, it was mentioned in the 

 '' Naval and Military Intelligence," that a certain naval oflicer had 

 seen the pole star from the Tropic of Capricorn (234 degrees south 

 of the Equator). It was in vain for intelligent persons present to 

 assert that this could not be. The lecturer insisted that it was so, 

 and for some time after he left Plymouth, many were actually per- 

 suaded that the earth is plane. At length some one was at the pains 

 to turn over the volumes of the Times in the Plymouth Library, and 

 then it turned out (as was to have been expected) , that the ship 

 from which the pole star had been seen (the fact was merely men- 

 tioned as part of log observations), had been indeed 23 J degrees 

 from the equator, but to the north instead of the south ! 



