352 REPORT — 1875. 



On. A. S. Hallidie's Wire Rope Traction-Bailiwaj. By W. Siiixir, Q.E. 



Oil a means of liecorcUng the Movements of Points and Sir/nals. 

 By ^Y. Smith, C.E. 



On a Breech-loading Mountain Gun. By W. Smith, C.E. 



On a Military Bidon. By W. Smith, C.E. 



On Portishead Doclc. By F. C. Stileman, C.E. 



Position. — The docks are situated on the eastern side of Portishead Hill, whicli 

 forms a most complete shelter, both to the dock aud approaches thereto. 



Pier and Outer Works. — A timber pier, having a double line of railway, 540 feet 

 in length, was constructed by the Bristol and Portishead Pier and _ Railway Com- 

 pany in the year 1870. The new works were commenced by continuing the line 

 of this pier for a length of 4-30 feet inland, completing nearly 1000 feet of outer 

 quay wall and pier. A return wall, forming the entrance to the docks, and in 

 which the entrance-gates will be erected, is also constructed. All this work has 

 been executed between the times of the tides, or " tidal work." 



Dam. — A temporai-y dam is formed across the future entrance, constructed of 

 wrought-iron girders built into the masonry and planked with timber. 



Interior JVorks. — The tide was excluded on the 10th June, a not sufficiently long 

 time to allow of the inner works being in '■ full swing." Some portions of the ex- 

 cavation are down to within 2 feet of the permanent level of the dock. The foun- 

 dation of the dock and wharf wall have been proved to consist of rock and marl. 



ZocJc. — The lock will be 660 feet in length, and 6G feet in width ; the sills are G 

 feet above U W. 0. S. tides, affording a depth at II. W. of 34 feet at 0. S. and 25 

 at neaps. 



Provision has been made for excluding the equinoctial tides by a caisson 

 (already built). 



Bock. — The wharf wall will be built (and is just about to be commenced) in the 

 same straight line as the outer wall for a length of ISOO feet. 



The area of the dock will be I25 acres, having a depth of 24 feet. In addition 

 to this, a considerable area covered by water will be available for timber ponds. 



Anchorage. — The well-known anchorage ground at King Koad is immediately 

 adjacent to the docks. 



Railway. — The Bristol and Portishead Railway, in connexion with the railway 

 system and these docks, was opened ia 18G7. 



0(1 Communication between Passengers and Guards. 

 By Messrs. SiROtrDLET & Rusbeidge. 



On Vertical Motion of Vessels. By John I. Thoentcroet. 



The present paper treats on some experiments made to ascertain the vertical 

 motion of a vessel relative to the undisturb ed water-surface. 



The experiments were made with a torpedo-boat, 67 feet in length and 85 

 feet beam, which had a speed of about 19 knots. The water-surface was measured 

 at three points respectively (1, 14, and 27 feet ahead of the launch) by suspended 

 weights adjusted to its surface, as suggested by Mr. Froude (see Plate XIII. fig. 3), 

 the inclination of the boat and revolutions of the propeller being at the same time 

 noted. 



The results are shown in the accompanying diagi-am (see fig. 4, Plate XIII.), where 

 the horizontal ordinates represent revolutions of the propeller per minute (240 to 

 one inch) ; the vertical ordinates of the line A, speed of screw ; vertical ordinates of 

 the curve B, speed of boat ; the curve C, inchnation of the vessel in 125 inches ; 

 the curve D, motion of centre of gravity relative to water-sm-face at rest ; the curve 

 E, mean reading of the weight No, 3 ; F, mean reading of weight No. 2 ; G, mean 



