430 



NATURE 



[March i, 1900 



be of great value in the Army and Navy, as reflectors for search- 

 lights, where the breaking of the mirror in lime of action might 

 have very serious results. 



In this article it has only been possible to touch the margin 

 of the electro-chemical industry, and only, with the exception of 

 calcium carbide, such processes as deal with electro-metallurgy 

 and electrolytical deposition have been dwelt upon. It is hoped 

 in another article to draw attention to the production of non- 

 metallic elements, and to the manufacture of chemical products 

 both inorganic and organic. F. Moi.LVVO Perkin. 



THE PROBLEM OF COALING AT SEA. 

 "VITAR, at the present time, brings home to us the necessity of 

 considering " Energy," its different forms, and their practical 

 application. In these days, when the machinery of a battleship 

 not only propels the vessel, but lights, ventilates, and controls 

 the working of the heavy guns, it may be said that the ship is 

 primarily dependent on one source of energy — Coal. A vessel 

 short of this requisite has hitherto been compelled to fall out of 

 line and be thus useless until she has "coaled ship," which in 

 many cases entails several miles steaming, delay, and perhaps 

 lost opportunities. 



On this account any efKcient mechanical contrivance for over- 

 coming the difficulty of obviating the ship putting into port and 

 enabling a full recharge of energy while cruising to be possible 

 must be looked upon by all with interest. 



In the Engineering Magazine for February is an illustrated 

 account of a series of trials made in the United States Navy 

 with the " Miller Conveyor " for coaling at sea, and the method 

 may be briefly described as follows : — 



The battleship to be coaled tows the collier, from which it 

 takes the coal in loads of 840 lbs. by means of an overhead cable 

 and suspended carriage. During the experiments two points of 

 interest presented themselves : (i) The proper distance between 

 the ships ; (2) The way of overcoming the variation required in 

 ;he length of ropes caused by the rolling and pitching. With 

 regard to the first point it was found that with 300 feet between 

 the ships, the collier would not follow properly, but during 

 the rough weather trial with about 400 feet between the ships, 

 the collier followed perfectly. 



The second point caused the chief difficulty, and in Mr. 

 Miller's design we find the length of overhead cables made 

 variable, as required partly by the movement of the ships them- 

 selves, and partly by the power engine on deck. In the following 

 table will be found information and data of the five trials 

 made : — 



Trial 

 Number 



[ Number of loads (840 

 Speed I lbs.) or tons trans- 

 shipped 



9 loads only 



Remarks 



Adjustments made 



Work stopped through lack of 

 skill on part of operator 



Work could have continued but 

 for lack of sufficiint crew to 

 fill the bags 



Between the third and 



1 3h. 43m. 



I 80 trips made in 80m. , 

 1 or 30 tons in ih. 20m. 



fourth slight alterations made 



Trial lasted four hours ; water 

 smooth, ground swell 



Could have continued indefi- 

 nitely. Board of Judges 

 satisfied. Water rough. 



As we are informed that the battleship consumed about 3^ 

 tons of coal per hour, the actual (or rather "paying") rate ot 

 coaling obtained was sixteen or seventeen tons. 



The behaviour of the apparatus in rough weather was 

 satisfactory, and the author writes, "The boats steered at first 

 head on to the sea, the forecastle of the battleship Massachusetts 

 was washed at every plunge, and no coal could have been 



NO. 1583, VOL 6j.] 



delivered there, even if desired. The course was then changed 

 quartering on the sea; the results were the same. Then the 

 boats steered in the trough of the sea, and the rolling did not 

 affect the working." 



The article, which is illustrated with ten good photographs 

 and a diagram, is certainly worthy of note, and deals with a 

 subject which it is possible will revolutionise naval warfare in 

 the near future. 



MERCURY AS A NAKED EYE OBJECT. 



U ARELY visible, and always difficult to observe satisfactorily 

 ■^^ in a telescope, this planet is yet a most attractive object to 

 the unaided eye. Not receding to a greater distance than 28° 

 from the sun, he is, however, never above the horizon in Eng- 

 land for a longer period than two and a quarter hours before 

 sunrise, or for a similar interval after sunset. When an evening 

 star in the spring months or a morning star in the autumn season, 

 he may often be caught and watched for an hour or so, shining 

 with a sparkling, rosy lustre, and presenting much the same 

 aspect as a fixed star. 



To secure a view of Mercury forms one of the earliest and 

 greatest ambitions of the amateur astronomer. Among his first 

 books there will sure to be a copy of Mitchell's " Orbs of 

 Heaven," or Dicks's "Celestial Scenery," and on reading the 

 statement that Copernicus never succeeded in seeing Mercury, 

 he re.solves that he will do his best to catch a glimpse of thi.s 

 elusive little "Messenger of the Gods." After some vain 

 attempts he finally succeeds, and it is not too much to say that 

 the spectacle .sometimes excites and gratifies the observer more 

 than any other subsequent event in his astronomical career. 

 Who is there among us who does not remember the thrill of 

 pleasure incited by the first detection of this fugitive orb, and 

 the conscious pride with which we realised that we had com- 

 menced our celestial work by achieving a feat which had beeri 

 denied to the greatest astronomer of the sixteenth century ? 



But, as a matter of fact, there seems to be considerable doubt 

 whether Copernicus ever really complained of failure to see 

 Mercury. There is evidence to show that he never expressed 

 himself in the manner quoted in many of our popular text -books. 

 There may, it is true, have been some ground for the statement, 

 but it is well known that a biographer has only to introduce a 

 special incident of the kind alluded to, or to unduly colour some 

 expression, and whether on doubtful evidence or not, U is liable 

 to be copied and recopied by subsequent writers without any 

 investigation until it becomes generally accepted as a fact. But 

 admitting for the moment that Copernicus really failed to discern 

 Mercury, he .seems to have had very good reason for it. His 

 residence was at Thorn, in Prussia, and through the valley near 

 ran the River Vistula, over which were frequent fogs which 

 obliterated objects near the horizon. 



This tradition about Copernicus and Mercury has certainly, 

 however, enhanced the interest with which the planet is re- 

 garded as a naked eye object. The beautiful white lustre of 

 Venus — incomparably brighter than the aspect of Mercury — 

 the stronger and steadier, yellowish light of Jupiter, or the con- 

 spicuous ruddy hue of Mars may present a more striking 

 appearance in the sky than the twilight-veiled splendour of 

 Mercury, but there is something about the sparkling lustre of 

 the latter orb, hovering fugitively on the brow of the horizon, 

 which forms an attraction peculiarly its own. 



The best time to observe the planet in igcxD will be during 

 the first eleven days of March, when his times of setting will 

 be as follows : — 



During this period Venus will be a very brilliant object, situated \ 



about 21 degrees E.N.E. of Mercury. The greatest elonga- j 



tion of the latter (18° 16' E.) will occur at 11 a.m. on March 8, J 



on which day he sets about ih. 50m. after the sun. If the j 



western sky is clear on March 2 at about 6 p.m. an exception- V 



ally good opportunity will occur for detecting the planet, for he \ 



