1846.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



91 



quired ; but if a brcezc should spring up, tlicn it will be necessary to increase 

 the speed of the propeller. To effect this the engine must he temporarily 

 detached by loosening the cliilch : the scionil pair of wheels must then he put 

 in gear, and the first put out of gear ; then upon connecting the engine again, 

 the speed of the propeller will be very uuich increased. — If the breeze should 

 freshen still more, the engine must he again detached, and the third pair of 

 wheels put in gear, the otlier.s being previously put out of gear ; as the wheels 

 jrjrjr all slide freely along the shaft this object is easily effected by the at- 

 tendant engineer. .\ friction brake / of the ordinary kind is mounted ou the 

 propeller shaft for the purpose of preventing it from revolving, while the 

 toothed wheels are being jmt in and oul of gear. 



The inventor also proposes sometimes to adapt the invention to tiie shafts 

 of paddle wheels, as exactly the same elTect may be produced therewith. 



A variety of other different plans might be devised of effecting the object 

 of the invention — viz. driving the propeller at different speeds according to 

 the speed that the vessel advances by nther means ; but the method he has 

 shewn above he believes to be the best, although be does not intend to confine 

 himself thereto. In figs. 2 and 3 is shewn a means of effecting tlie same 

 object, by means of cones, pullies, or drums, and which may under certain 

 circumstances be found useful. The speed of the propeller is regulated by 

 moving the band along the cones, pullies, or drums, one set of which must 

 be mounted on or connected to the engine shaft, and the other on the pro- 

 peller shaft, which passes through the stern post of the vessel, as usual when 

 this description of iirnpeller is employed. 



To reduce the frictions at the bearings the inventor introduces a number 

 of anti-friction rollers placed around the shaft, and allowed to revolve both 

 CD their own axis, and also round the shaft itself. The bearings are pro- 

 vided with proper packing to prevent the water from entering the vessel. At 

 M n, fig. 1, is a bearing for resisting the horizontal thrust of the propeller 

 shaft when in rapid rotation. This bearing is shewn upon an enlarged scale 

 at figs. 4 and 5, fig. 4 is a view looking from above, and fig. 5 a transverse 

 vertical section. The bearing consists of a metal box screwed to a stationary 

 framing, the pin o hears against one end of the shaft c c, and can be tightened 

 as may be required. The metal box n is filled with water until about half of 

 the end of the shaft c is immersed, and then a quantity of oil is poured in, 

 wliich always floats at the top ; the cock p is for ascertaining the level of the 

 two liquids. I3y constructing the bearing in this manner it is kept cool, as 

 the water in the box will .ibstract the heat from the working parts and pre- 

 vent them from getting overheated. 



The second part of the invention is for improvements in the construction 

 of propellers ; it consists in mounting any convenient number of straight 

 blades at an angle round the shaft, in such a manner that the angle may he 

 varied according to the speed at which the vessel is required to progress. 

 The angle is regulated by a ring, firmly connected either to the propeller 

 shaft or to radial arms which carry the propellers, and made to turn round 

 on a point, so as the ring is moved round on its axis; it either screws in or 

 forces out the outer ends of the arms, and by that means alters the angles of 

 the blades. 



The claim is, first for the employment of differential gearing of any de- 

 scription whereby the speed of the propeller, or propeller shaft, may be in- 

 creased or diminished according to circumstances without altering the speed 

 of the engine. Secondly, the adaption or application of a number of rollers 

 round the propeller shaft in the hearing in the stern post, and also the mode 

 of constructing the end bearing, and keeping it cool by means of wafer and 

 oil as above shewn and described : and thirdly, the improved construction of 

 propeller described, whereby the angle of the propeller may be varied accord- 

 ing to the speed of the vessel. 



AZIMCra AND STEERING C0.MPAS3, 



Edwabd John Dent, of the Strand, London, chronometer maker, for 

 " Improvemen/s in ship's compasses." — Granted July 30, 1S44 ; Enrolled 

 January 30, 1845. 



Amongst the evils arising from the present construction of compasses are 

 the following: — 1st. The friction arising from the imperfect mode of suspen- 

 sion ; which is that of a hollow cup in centre of the needle, resting upon a 

 steel point ; in which case it is obvious that a want of horizontality in the 

 card will cause considerable friction between the convex sides of the pivot 

 and the sides of the cup. 2ndly. \ considerable error is caused by the as- 

 sumption, that the magnetic a.ris of the needle coincides with what is called 

 the maker's aris, which is the line determined by the marks or zero points 

 on the extremities of the needle; which error in flat needles, such as are 

 usually applied to compass-cards, is frequently of such maguitudc as to be 

 quite inadmissible, even in compasses for common purposes, much less for 

 those intended for accurate experiment. 3rdly. Another source of incon- 

 venience and inaccur.icy arises from the unequal amount of inertia as regards 

 the axis, or hoiizontal line drawn through the centre of the card, about which 

 line it is compelled to vibrate or deviate from its horizontal position by mean^ 

 of the alternate pitching and rolling of the vessel. However well the gynibal 

 apparatus, in fbicb the card is placed, is balanced, yet as the card has a 

 motion or time of vibration to itself, depending upon the position of the axis 

 of its vertical vibrations with respect to the axis of the needle — which vibra- 

 tions are not altogether under the control of tlie gymbals although its vibra- 

 tions are coiitinually checked, and its quiescence disturbed by it in conse- 

 quence of the supporting pia coming in contact with the sides of the cup, as 



before mentioned — yet in the construction of the binnacle compiss, the card 

 ever will be subject to irregular deviations from the horizontal plane, arising 

 from this cause. 



1 be mode by which the inventor has removed these evils has been by al- 

 tering the nature of the suspension ; that it, by suspending the card in a 

 similar way to the balance of a chronometer, and with equal delicacy, both 

 ends of the pivot acting on diamonds, and the boles jewelled, by which means 

 the card is constrained to move very nearly in the horizontal plane, since in 

 this respect it is entirely under the control of the gymbals. The friction is 

 also considerably reduced by this mode of suipensiun. The great accuracy 

 with which the card returns to the same position has been clearly shown by 

 a great number of experiments. To remove the error arising from the non- 

 agreement of the marked or maker's with the magnetic axis, a siin|dc con- 

 trivance is effected for the inversmn of the card, so that either side of it may 

 be placed nl/ove or l/elov. Since the marked axis of the needle is in each of 

 these positions at equal distances from, but on opposite sides of the magnetic 

 meridian, a mean of an equal number of observations in both positions of the 

 card will evidently eliminate any error of this nature, and give the true mag- 

 netic azimuth of f he observed object, at the lime uf observation, by aji equal 

 compensation of error. It is also plain that the constant adjustment re- 

 quired to make a delicate needle horizontal in different magnetic latitudes is 

 rendered thus unnecessary. 



DOCKINS'S PATENT HEMITROPE, 



Or Double Wedged Blocks, applicable to Paving and other purposes in Wood 

 and Stone. 



In casting our eyes over those leading streets of the metropolis now paved 

 with wood, we find a something wanting in all of them, and this want is so 

 pal|iably manifest to even common observers as to endanger the existence of 

 all the patents now in operation. There is an evident want of unity in design 

 and execution, a neglect or want of knowledge of the minor details and 

 finish ; thus one patent is too complicated and consequently too expensive, 

 another fails in the absence of or in the use of concrete, another destroys 

 itself by its own expansive powers ; in short, objections start up on every 

 side, which are but too readily laid hold of by those autcdeluvians who sigh 

 for the good old times when the stones were disposed to wage perpetual war 

 with tender feet, relieved only by occasional deluges of mud. The principle 

 of M'Adara was unphilosophical, it was a mechanical method of rapidly con- 

 verting granite into mud, the stones being broken small, sand added thereto 

 and water nd libitum ; a principle equally inconsistent applies to the wood 

 pavements now laid down, concrete or no concrete, the bed is laid down 

 without reference to carrying off the excess of moisture in this excessively 

 wet climate of ours, the wood is chosen for cheapness and not for durability, 

 and laid down and grooved ; it is then made the receptacle of every kind of 

 filth, as though the end and aim of the patentee was to rot it as soon as 

 possible ; even the surface grooving is clumsy and unscientific, for the un- 

 protected perpendicular fibres being soon beaten down by heavy vehicles, the 

 grooves in wet weather are immediately filled up, and aided by the mud 

 become equally dangerous to man and beast. Cleanliness would do much 

 towards preserving the wood, but street cleanliness is of late little attended to. 



We have been led to these reflections by a perusal of the patent now 

 before us. 



An idea of the shape of the block may be fortiied by supposing one of the 

 triangles of an equilateral triangular prism to be turned 60" on the a.xis of 

 the prism. If new lines of junction be now drawn between the angles of the 

 opposite triangles, the three rectangular sides are converted into six triangles, 

 the alternate bases of which are the sides of the primitive triangles. The 

 plain of the six triangular sides inclines outwards from the base towards the 

 apex by an irregular quantity, which diminishes as the length of the axis in- 

 creases. A section of this solid taken through the centre of the axis, and at 

 right angles to it, would present a regular hexagon; but, if equal quantities 

 are cut off at each end by sections at right angles to the axis, the remaining 

 central portion of the solid is precisely in the form of Mr. Dockins's block; 

 the two ends, that is the base and upper surface, being irregular hexagons 

 with equal alternate sides, and the other six sides of the block being equal 

 and similar trapeziums. 



A vertical section of the block bisecting two opposite sides of the irregular 

 hexagon will present a rhomboid ; and if the block be turned on its axis, 

 and similar sections be taken at intervals of tJO^, the rhomboids will incline 

 alternately in opposite directions. It is on that peculiarity in the form of 

 the blocks that the patentee principally relies for their eflicacy in supporting 

 each other and maintaining an even surface, three sides of each block being 

 so inclined as to rest on the surrounding blocks, and the other three sides 

 inclined the reverse way preventing the blocks from rising, as the short sides 

 of the hexagons at the surface coincide with the central parts of the long 

 sides of the adjoining bexagonj; small triangular interstices are left which 

 may he filled up with grouting, nflbrding by this means a footing for horses. 

 The accompanying diagrams will elucidate this form more fully. 



Fig. I is an isometrical, and lig. 2 a lioear bird'n eye vievr. lu fig. 2 tha 



12* 



