KNOAVLEDGE 



[AnG. 21, 1885. 



festly share tlie charges of the parts of the cylinders to 

 which they belong, and equally manifestly, they are 

 therefore repelled by the respective cylinder- ends. The 

 two central balls are not only repelled by the cylinders, 

 but, being oppositely charged, become mutually attractive. 

 If D be touched with the finger, the positive electricity 

 at the distant end will, as in the experiment i^jith the 

 eggs, be neutralised, and the pith ball in proximity 

 will also losG its charge, whence it will fall into the 

 vertical position. Similarly, the finger being withdrawn, 

 and the adjacent ends of the two cylinders brought into 

 contact, will result in a further neutralisation, and the 

 two central balls will also hang vertically. C D will 

 then act as one long cylinder, a greater degree of electri- 

 fication will probably be produced at the negative end of 

 C, and a iJositive charge will in consequence appear at 

 the distant end of D equal in quantity to the increase of 

 negative on C. Other experiments with these cylinders 

 may be inferred from the experiments with the eggs. 



DUAL GENERATION. 



Pr. 5. — The two electric states are always produced 

 together and in equal quantity. 



To one conversant with the nature, or rather the 

 behaviour, of electricity, this requires no demonstration. 

 It is well, however, for beginners to have it always in 

 mind. The induction experiments which we have just 

 performed demonstrate the fact pretty clearly, and 

 enjphasis was laid upon it in Pr. 1 . 



Ex. cm. — Rub a stick of sealing-wax with a piece of 

 flannel or a pad measuring about 5 inches by 4 inches, 

 and composed of five or six layers of flannel 

 sewed together. Let the flannel be insulated fi-om 

 the hand by interposing a piece of sheet gutta-piercha 

 (procui'able at most of the shops where gutta-percha 

 goods are sold). Either the sealing-wax or the flannel 

 will then be found electrified, although oppositely. That 

 their charge is equal may be proved by presenting both 

 bodies together to a suspended pith ball. The absence of 

 attraction proves the equality; for were one charge 

 greater than the other, that one would exert a prepon- 

 derating influence and cause attraction. 



THE ISLE OF WIGHT STEAII 

 FERRY.* 



THE works at Langston Harbour, near Portsmouth, 

 and at Brading, in the Isle of "Wight, designed to 

 efiect the transport of trains of railway vehicles across 

 the Solent, were completed on the 5th inst., and on 

 the following day the appliances which have more than 

 once been used jarovisionally during the execution of the 

 works, were pronounced ready for regular trafiic. It 

 should be stated that no claim is laid to mechanical 

 novelty — the merit lies in the ingenuity in which 

 commonplace mechanical arrr.ngements have been ap- 

 plied to achieve in a simple way an exceedingly useful 

 jjurjiose. Railways existing on the mainland and in 

 the Isle of Wight, with their Unes coming down to the 

 seaside, the problem to be solved was how to transfer 

 simply, cheaply, and expeditiously fi-om the railways 

 to the deck of seagoing vessels, railway vehicles with- 

 out disturbance of their load. Once upon the deck 

 of the steamer, supposing only she be adapted to 

 the carrying of a heavj^ deck load, the transport is 



* From Engineering. 



simple enough — the thing is the loading and unloading, 

 and to be useful this must be accomplished by means 

 more expeditious and less costly than the ordinary 

 method of handling and (i-.m^liinmi'iil . Tin ■ distance to 

 be traversed between i; ' • ■ ■■ i !. ■ i ■ is between 

 ten and eleven miles, i'-[ ; i'. , ; ' . . ; . u .sea, the 



rest in land-locked hwrl ■ .' . ! . . i li i i-lniid, as on 



the mainland, liv,. 1 . . :, i ; ']•■' ' , , Imxii as tlie jilaces 

 of arrival ainl ! , m |, j,l,s the process of 



loading and in' Hij .- ii [ m i-fectly still water, 



and on both till i:s . iiii.iiii I :■ 1 r i j. im nts are the same. 

 The amount of structural work on the island was rather 

 less than that necessary on the mainland, owing to some- 

 what less favourable conditions at Langston. It goes 

 without saying that on both sides there is direct physical 

 connection with the railway systems. At Brading all 

 the railways in the island are communicated with, while 

 at Langston access is obtained to the Hayling Island 

 branch of the Brighton and South-Coast Railway, which 

 at Havant has a junction with the London and South- 

 Western system — to London by the direct Portsmouth 

 line as well as to Southampton and the West of England. 



At Langston the railway skirts the sea. Alongside of, 

 and parallel to, the railway and upon the foreshore an 

 embankment has been built about 700 yards in length, 

 and of width varying from 30 to 40 yards. The side or 

 sea-face of this embankment is sloped and jntched in the 

 customary manner for its entire length, save 300 ft. at 

 the extremity, where a wharf is formed suitable to the 

 use for loading and discharging of ordinary sea-going 

 craft. From the end of the embankment a sloped timber 

 jetty projects, commencing at the rail level and descend- 

 ing by a gradient of 1 in 8 to 4 ft. below the natural bed 

 of the sea. From the top to the bottom of this slope are 

 laid eight ordinary permanent-way rails, four of which 

 constitute two running lines of the standard gauge, and 

 along whicii, as presently explained, the railway vehicles 

 pass, and four laid close, and jDarallel, to each of the 

 running rails. These latter act as check rails, but fulfil 

 also a more important purpose to be described. 



In carrying the waggons on board the steamer, they 

 are placed upon two lines runnLiig from stem to stem. 

 In discharging and loading them, the vessel approaches 

 the sloping jetty stern on, bringing the parallel rails 

 upon her deck into line with the rails laid upon the sloping 

 jetty. It follows that when the tide is high and covers 

 the greater part of the slope, the level of the steamer's 

 deck approaches the level of the top of the jetty ; when 

 the tide is low, the steamer approaches at a lower level, 

 and a considerable part of the slope is exposed ; but 

 neither at high or low tide can the stern of the steamer 

 be brought sufiiciently near to the fixed slope to admit 

 of waggons passing from the one to the other. There is 

 always a hiatus which must be bridged. The four extra 

 rails above mentioned are useful in this connection. They 

 carry the moving bridge or cradle, which, passing up and 

 down the sloping jetty in the varying states of the tide, 

 connect the ship, at whatever height her deck, with the 

 rails on shore. 



'ted on twenty wheels, 

 jf the jetty, is of 



ichn 



nits 

 L' balai 



and 



ed s 



ist-i 



; to 



It is moved 

 3 of drawing engines, 

 which also drive two horizontal drums 3 ft. in diameter, 

 means of which waggons are lowered on to and 

 wn up from the deck of the steamer. The drawing 

 ines are a pair of ordinary winding engines of 60-h.p. 



