208 



NA TURE 



[July 2, 1903 



Observations made in order to determine whether the light 

 of this Nova exhibite<^ the change of focus observed in the 

 light of Nova Persei gave at first, negative results, but 

 careful observations made on April 27 indicated that the 

 light of the Nova, when compared with that of an ordinary 

 star, showed a difference of +008 inch (a-oomm.) in focus. 



The crimson image observed on March 30 had disappeared 

 on April 27, the out-of-focus image of the Nova then re- 

 sembling that of an ordinary star. Cloudy weather at 

 Yorkes from April 7-27 prevented Prof. Barnard from de- 

 termining the exact date at which this change took place. 

 The magnitude of the Nova is exhibiting the same peri- 

 odical fluctuations as were observed in the case pf Nova 

 Persei. 



The Red Spot on Jupiter.— In No. 3875 of the Astro- 

 nomische Nachrichten, Mr. Stanley J. Williams describes, 

 and gives the detailed results of, "his observations of the 

 " great red spot " during the opposition of 1902. 



Transit observations of the middle of the spot gave a 

 rotational period of yh. 55m. 39555., and of the " follow- 

 ing " end of the spot yh. 55m. 39-885. ; taking the weighted 

 mean of these observations, Mr. Williams obtains, from 

 275 rotations, gh. 55m. 39.66s. as the result. This shows 

 a further considerable acceleration of the rotational period 

 of the red spot, amounting to 1-265., as compared with the 

 result obtained during the opposition of 1901. 



The Study of very Faint Spectra.— In a dissertation 

 publishedjn No. 35 of the Lick Observatory Bulletins, Mr. 

 Harold K. Palmer describes an arrangement whereby the 

 Crossley reflector has been adapted to the study of very 

 faint stellar and nebular spectra. 



The work was first suggested, but not completed, by 

 the late Prof. Keeler for the purpose of obtaining, amongst 

 other spectra, the spectrum of the faint central star of the 

 ring nebuia in Lyra. 



A modified form of Prof. Keeler 's proposed spectroscope 

 has now been adopted, and the results obtained with it are 

 very satisfactory ; its essential features are as follows :— 

 A concave quartz lens intercepts the converging beam of 

 light from the large mirror, and renders the rays parallel ; 

 these parallel rays are then refracted by a 50° quartz prism 

 and are focused on to the photographic plate bv a convex 

 quartz lens placed between the prism and the plate. The 

 two lenses and the prism each have an aperture of 25 mm. 

 An arrangement attached to the prism cell allows the prism 

 to be moved to one side, so that the spectroscope may be 

 focused for the incident light by means of an eye-piece 

 which carries a finely divided scale, and another eye-piece, 

 placed at the side of the movable slipping plate, allows the 

 • following " during exposure to be performed in the usual 

 manner. 



Spectrograms of such faint objects as the stellar nebula 

 NGC 6807 (magnitude 13), the Novae in Perseus (looi) 

 Auriga and Cygnus (1876), and the Wolf-Ravet star No. 43 

 have been obtamed with exposures varying from one to 

 four hours, and show a fair amount of detail. 



Three spectrograms of the ring nebula were obtained, 

 two with thirty minutes' and one with two hours' exposure' 

 but the only trace of the central star is a faint line which 

 appears on all three plates, and, in the longer exposure 

 shows a faint dot in a position a little to the more rel 

 frangible side of the condensation A 373 in the nebula ring. 

 A detailed description of each of the spectra obtained is 

 given in Mr. Palmer's paper. 



INSTITUTION OF NAVAL ARCHITECTS. 

 'P HE Institution of Naval Architects held its summer 

 meeting this year in Ireland, commencing Tuesday, 

 June 23, when the opening meeting was held in Queen's 

 College, Glasgow, the president of the Institution occupy- 

 ing the chair. 



After the usual formal proceedings, in which the members 

 were welcomed to the city by Sir Daniel Dixon, the Lord 

 Mayor of Belfast, and the Rev. Dr. Hamilton, president 

 of Queen's College, three papers were read. The first was 

 by Mr. C. F. L. Giles, the engineer to the Belfast Harbour 

 Commissioners, and gave a brief description of the harbour 

 and its development. Mr. E. H. Tennyson D'Eyncourt 

 followed with a paper " On Fast Coaling Ships for our 

 NO. 1757, VOL. 68] 



Navy." The author proposed that certain vessels should 

 be built specially to wait on the fleet and supply it with 

 coal in time of war, and they should be fitted with appli- 

 ances for transferring the fuel to the warships at sea. 

 These vessels should be able to steam 17 knots easily and 

 continuously, and 18 knots in case of emergency. They 

 would have to be of considerable size, therefore, and would 

 be loaded with 10,000 tons of coal, besides that needed for 

 their own use. The author estimated that the requirements 

 coulcf be met on a length of 550 feet, a beam of 66 feet, and 

 a draught of 27 feet with 10,000 tons of coal on board ; that 

 would enable the vessels to get through the Suez Canal. 

 The horse-power necessary for 17 knots would be about 

 12,000. With quadruple engines the consumption of coal 

 would be i^lb. per I.H.P. per hour, so that at full speed 

 the collier could go 1000 miles from the coaling station 

 and back on 800 tons of coal, carrying 10,000 tons of coal 

 ior the use of the fleet. That would be sufficient to coal 

 completely five of our largest battleships or cruisers, or, if 

 needed, ten such battleships could have their bunkers half 

 full. 



Comparing this with the present conditions, it would 

 take one of our large cruisers or ironclads four or five days 

 to make the 2000 miles, and she would lose at least 1000 

 tons of coal, and have to be steaming hard all the time. 

 The vessel would arrive with dirty boilers, a tired comple- 

 ment of stokers, and the greater part of her coal already 

 burnt. In ordinary peace time the colliers could be used 

 for taking coal to the coaling stations. The cost of these 

 vessels, fully equipped, with Temperley transporters and 

 all the necessaries for quick coaling, would be about 

 270,000^. each, so that four or five could be built for the 

 cost of one first-class armour-clad or cruiser, whilst four 

 could be kept in commission for about the cost of keeping 

 up an armour-clad. In time of war, the author claimed, 

 each collier would be equal' to several additional warships, 

 as it would enable so many of the latter to remain at sea, 

 saving them the time of going to and fro for coal, and 

 giving them an opportunity to clean their boilers and do 

 minor repairs to the engines, besides resting the whole 

 crew, officers and men. In the discussion which followed 

 the reading of this paper, it was pointed out that it was 

 more reasonable to transform a mercantile vessel into a 

 collier in time of war than to build such vessels purposelv 

 for an occasion that might never arise. 



Mr. James Hamilton, of Glasgow, next read a paper in 

 which he described an ingenious means which he had de- 

 vised for converting a moderate speed steamer into one of 

 very high speed for war-like purposes. He pointed out 

 that the extreme speed now demanded by the Admiralty 

 for the new mercantile cruisers to which it was proposed 

 to give subsidies was higher than could be used, with profit 

 to the owners, during peace time for ordinary Transatlantic 

 service. The Admiralty asked 25 knots ; Mr. Hamflton 

 put the limit for mercantile use at 22 knots. If engines 

 are not worked up to the power for which they are de- 

 signed., they are uneconomical in themselves, whilst for 

 excessive speeds very great engine power is needed. In 

 order to solve this difficulty, Mr. Hamilton proposes triple- 

 screw steamers, with one central screw and two wing 

 screws. For the 25-knot speed all three screws would be 

 used, and their respective engines would therefore be at 

 work at their full power, and so be operating economically : 

 for the 22-knot speed the two wing screws only would be 

 used, and in order to prevent the drag of the central, idle 

 propeller, the latter is drawn forward, with its shaft, until 

 thi blades of the screw touch the stern-post of the ship. 

 This stern-post _ is so formed that the blades lie snugly 

 against it, and in this way the resistance of the water flow- 

 ing past the idle propeller is got rid of. For a four-bladed 

 screw the stern-post is made of cruciform shape by the 

 addition of two horizontal wings. In the discussion on the 

 paper, it was pointed out that the shape of the stern-post 

 was not favourable to speed on account of the eddy-making 

 resistance. Mr. Hamilton, in reply to the discussion, said, 

 however, that the objection was not of so serious a nature 

 as was supposed, supporting his contention bv diagrams 

 illustrating the stream-line theory. 



On the second day of the meeting, Wednesday, June 24, 

 Prof. J. H. Biles read a paper " On Cross-Channel 

 Stearners," in the course of which he gave particulars of 

 certain vessels, and discussed the different qualities needed 



