18fi 



- KNOWLEDGE • 



[Aug. 29, 1884. 



equidistantly in a small diaphragm at the focus of a telescope's 

 eye-piece might ansiver very well in fine weather ; but, recollect, 

 sir, that such weather does not always prevail ; nor is the ship at 

 all times steady enongh to use a telescope thus fitted. In fact, 

 there are really such bad nights, when it is blowing and raining 

 liard, and sprays are drenching the ship fore and aft, when glasses 

 cannot be used at all, and we must trust to our own unaided powers 

 of sight. 



Experience has taught me that the plan suggested by " J. H. G." 

 of carrying a white light under a coloured one has this objection, 

 that the white light outshines the coloured one. I have often 

 observed, when meeting steamers at sea by night, a white light 

 placed in a position where I expected to see the coloured one, and 

 which ought not to have been there at all, shining so brightly that 

 I could not detect the presence of the coloured one above it till 

 nearly abreast of the steamer, and at no great distance from her. 



With your correspondent " Chas. Rice's " plan, we could not tell 

 which side of the ship was presented to us, as the lights on each 

 side, when seen from before the beam, would be all of the same 

 colour. 



I think the lights as at present carried by ships, with the addition 



I will presently name, would answer the purpose, and all others 

 should be effectually screened or put out, so that they might not 

 be misleading, perhaps fatally so. 



Many of your readers know that the lights carried by sailing 

 vessels are a red light on the port or left side, and a green one on 

 the starboard or right side, each visible over an arc of ten points, or 

 112° 30', from right ahead. Steam vessels carry a white light on 

 the foremast head as well, visible over double this arc — that is, 

 from right ahead to 112° 30' on each side. The addition I would 

 make is to have two red lights placed vertically about six feet 

 apart, and about ten feet lower than the white light of steamers, 

 and on the after part of the after-mast, or in some such promiuent 

 position, visible through an arc of fourteen points, or 159° 30'— that 

 is from right astern to seven points on each side, thus overlapping 

 the other lights, and all being visible together through one point, or 



II 15'. The two vertical red lights to be carried in both steam 

 and sailing vessels, and by means of which we could always see 

 when we were overtaking another vessel.' 



I may inform your readers that as soon as a ship's light is seen 

 at sea, its direction and colour will always show whether it is on 

 the danger side of the observer, and the plan always adopted when 

 fii-ot seen of taking its bearing, and a few minutes afterwards 

 taking another, and noting the difference (if any) will show which 

 ship is crossing the other; if there is no difference, it shows the 

 ships are meeting, and there are proper rules by which one gives 

 way while the other holds her course, and we never aim at passing 

 as close as two hansom cabs in a street. 



It is always the practice, as well as the constantly-repeated 

 order, to give all vessels seen, especially at night, a wide berth. A 

 vigilant look-out carefully kept by the officer of the watch, as well 

 as those two most excellent qualities, a clear comprehension and 

 a ready resource, will, in all cases where appliances are not faulty 

 and the atmosphere fairly clear, keep any ship from collision with 

 another. It is further greatly to be desired that under equal con- 

 ditions all ships' lights should bo visible the same distance. 



There is also great need of distinction between the lights carried 

 by disabled ships and telegraph ships laying or repairing telegraph 

 cables. There being none at present, other ships are often taken 

 miles out of their course to find, instead of a ship in distress, a 

 telegraph ship at work. 



The three red vertical lights visible all round the horizon, and 

 which are carried in the place of the white masthead light, in tele- 

 graph ships at work might be changed to white. 



The light carried by a sailing pilot vessel is the same as that of 

 a ship at anchor, so that it is difficult at times to tell in what 

 direction the pilot-vessel is going ; it should be made obligatory to 

 carry the red and green lights on each side, the two red vertical 

 lights astern, and in addition, a red, white, and green light at the 

 masthead, separated about six feet from each other, and visible all 

 round the horizon, as well as to use the flare-up light as at 

 present, which latter would show when they were on station with 

 pilots aboard. A British Shipmastee. 



THE SPECTROSCOPE AND WEATHER FORECASTING. 



[1376] — Not long ago I invested in a Grace's Spectroscope, being 

 fond of the study of meteorology, and anxious to prove for myself 

 the accuracy of the accounts given in Knowledge relative to the 

 interesting instrument, and its power of predicting rain. My 

 object in writing this note to you is to state my gratitude to Know- 

 ledge for introducing the Spectroscope to me as an aid in the 

 prediction of the weather. I have effectually proved the im- 



portance and reliability of the instrument by this time. The 

 following instance of its validity is so conclusive that I venture 

 to inform you of it. 



A few days ago the weather was very unsettled here (as ii 

 still is), and there had been much rain in the early part of a 

 certain day ; towards evening, however, it cleared np a little, 

 but on asking the keepers, gillies, and sailors about what the% 

 thought the morrow would be like, they all agreed in saying 

 there would be " a lamp o' rain." The glass was falling, wind 

 was N.W. I then referred to my Spectroscope, and was much 

 surprised by its appearance, which only showed an extremely 

 faint rain -band. So confident was I of my instrument, that in 

 spite of disagreeing with all the weather-wise people of the 

 neighbourhood, I predicted there would be no rain for forty-eight 

 hours, and I proved, or rather the Spectroscope was, quite correct ; 

 not a drop of rain did we have, though the weather continued 

 to be most unsettled, and the aspect of the sky very threatening. 

 I may venture to say that the people (natives) about here (contrary 

 to custom) are very weather-wise, and are seldom out to any sxtent 

 in their judgments. 



County Antrim, Ireland. H. M. McI. 



AUGUST METEORS. 



[1377] — Several meteors were observed here on the 11th, 

 between lOh. 15m., and 12h. p.m. .\ttention was directed almost 

 exclusively to the constellations Cassiopeia and Perseus, no attempt 

 being made, except in two instances, at estimating the duration of 

 visibility. The first, seen at lOh. 23m., surpassed all subsequent 

 ones in brilliancy. It emanated from right ascension 2h. 57m.. 

 declination 51°, moved slowly towards /3 C'amelns, exhibiting alonj; 

 the whole track a phosphorescent haze, and after attaining its 

 maximum brilliancy, disappeared from view in right ascension, 

 ■ih. 40m., declination, 60° ; after having been visible for fully six 

 seconds. It was immediately followed by one whose path, when 

 prolonged backwards, came close to v Perseus. At lOh. 48m., one 

 appeared from between v and ij Perseus, described a path 6" long, 

 and faded near 9. At llh., a bright one, equal to a star of 1st 

 magnitude, came from right ascension, Ih. 40m., declination 6-1 , 

 and disappeared close to 32 Cassiopeia ; the path appeared to be 

 foreshortened, llh. 31m., one emerged from i Cassiopeia, and was 

 lost to view near r) Perseus; it was followed at llh. 5lra., by one 

 that appeared in right ascension tih., declination 75°, and dis- 

 appeared close to K Draco. Between llh. 51m., and 12h. none were 

 detected. 



Clouds prevented observations on the 12th. On the 13tb, at 

 lOh. 10m., one came from X Perseus, and disappeared close to^; it 

 was followed by one at lOh. 21m., that came from Mirfak, and dis- 

 appeared in right ascension 2h. 52m., declination 47°. At lOh. 46m. 

 one came from Algol, and travelled 9° in direction of f Persens ; 

 this was followed at lOh. 48m. by one from a point 1° north of Algol, 

 that disappeared near k Persens ; llh. 40m. appearedfrom direction 

 of 50 Cassiopeia, disappeared near 6. At llh. 50m. a very bright 

 one traversed a path that can be represented by a line drawn from 

 /I Andromeda, midway between i; and I, to right ascension Oh. 25m., 

 declination 30°. The luminous train continued visible for three 

 seconds. 12h. 8m., the last observed, appeared near ■■!/ Cassiopeia, 

 and was lost to sight near v Camelus. 



The above-mentioned are only a few whose paths were determinetl 

 accurately. A great many more were seen, but, owing to the 

 rapidity of flight, combined with the diminution of luminosity by 

 moonlight, their respective courses could not be traced with a suffi- 

 cient degree of certainty necessary for projection. On the 12th the 

 radiant for the Perseids lay near 45° + 53°, and on the 14tb 

 50° + 49°. Theoretically, its position is 51° -t- 55°. 



Liverpool, Aug. 16, 1884. W. K. Bkadgate. 



THE SATELLITES OF MARS : A COINCIDENCE. 



[1378] — Is it not truly noteworthy that Swift, in his " Voyage 

 to Lapnta," should have written: "They have likewise discovered 

 two lesser stars, or satellites, which revolve about Mars, whereof 

 the innermost is distant from the centre of the primary planet 

 exactly three of his diameters, and the outermost five ; the former 

 revolves in the space of ten hours, and the latter in twenty-one 

 and a half" ? 



I do not recollect whether the Laputan observers were right, or 

 nearly so, as to distances ; but if not, the discovery of these moons' 

 existence in the middle of the eighteenth century is sufficiently 

 striking. Simplex. 



[It must not be assumed that the Dean of St. Patrick's was 

 speaking of an actual discovery in the words which "Simplex" 

 quotes. In reality, Phobos, the satellite nearest Mars, is only 

 about a diameter and a half of the planet from his centre, and 



