1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



303 



permission of the Port of London Improvement Committee, in the 



corporation moorings, on the upper outside moorings off' the East 

 India Dock entrance at BUrkvvall, since the ISth of October, 1841, 

 carrying in that deep and rapid reach of the river nearly two tons of 

 mooring chains, and sustaining at its ring some of the largest ships 

 that enter those docks during the whole of that severe winter till the 

 autumn of last year. In spite of this severe work, and the fact that 

 it has not had or required a sixpence outlay in repairs, it is as buoy- 

 ant as ever. 



NEW INVENTIONS AND IMPROVEMENTS. 



REFLECTING LANTERN HELIOTROPE. 



Description of a Reflecting Lantern and a Heliotrope, used bij Major J. D. 

 Graham, as meridian marks for great distances, in 18-11, while tracing, in 

 his capacity of V. S. Commissioner, the due north line from the monu- 

 ment at the source of the river St. Croix. — (From the Proceedings of the 

 American Philosophical Society.) 



The lantern was constructed by Messrs. Henry N. Hooper & Co., of 

 Boston, under Major G.'s directions. It was similar in form to the Parabolic 

 Reflector Lantern, sometimes used in lighthouses, but much smaller, so as to 

 be portable. 



The burner was of the argand character, with a cylindrical wick, whose 

 transverse section was half an inch in diameter, supplied with oil in the 

 ordinary manner. This was placed in the focus of a parabolic reflector, or 

 paraboloid, of sheet copper, lined inside with silver about one-twentieth of 

 an inch in thickness, polished very smooth, and bright. The dimensions 

 were as follows : — 



Inches. 

 Diameter of the base of frustrum of reflector .. .. .. 16 - 



Distance of vertex from base . . . . . . . . . . . . 3'75 



Distance of focus from vertex . . . . . . . . . . 2-25 



Diameter of cylindrical burner . . . . . . . . . . '50 



Diameter of a larger burner, which was never used, but which, by an 



adapting piece, could be easily substituted . . . . . . 1*25 



The instrument answered the purpose for which it was intended, admira- 

 bly well, and was of great use in tracing the due north line. While it occu- 

 pied the station at Park's Hill, 15 feet above the surface of the ground, or 

 828 feet above the sea, in the latter part of September, and early part of 

 October, 1811, the light from it was distinctly seen with the naked eye at 

 night, when the weather was clear, from Blue Hill, whose summit, where 

 crossed by the meridian line, is 1071 feet above the sea; the intervening 

 country averaging about 500 feet above the sea, and the stations being 30 

 miles apart. 



The light appeared to the naked eye, at that distance, as bright, and of 

 about the same magnitude, as the planet Venus. Viewed through the 

 transit telescope, of 43 inches focal length, it presented a luminous disc, of 

 about thirty seconds of arc in diameter. From its brilliancy at that distance, 

 Major G. has no doubt that it would have been visible to the naked eye at 

 50 miles, and through the telescope at 100 miles, could stations, free from 

 interposing objects, have been found so far apart. 



It was remarked, that the wick employed by Major G. was considerably 

 smaller than that usually made, even for parlour lamps ; and to this cause he 

 attributed, in a great measure, the perfection with which the parallel rays 

 were transmitted from the reflecting parabolic surface, so as to make them 

 visible at so great a distance. Though a greater quantity of light is 

 generated by a larger wick, the portion of rays reflected in a direction 

 parallel to the axis, and which alone come to the eye, is the smaller as the 

 flame transcends the focal limit. The size of wick most advantageous for 

 use, may easily be determined by experiment : Major G.'s impression is, 

 that the smaller its transverse section, provided it is only large enough to 

 escape being choked up by the charred particles, even one-third, or perhaps 

 one-fourth, of an inch, the farther the light would be visible. 



It has occurred to Major G. that lanterns of this description might be 

 used with great advantage as station marks, in extensive trigonometrical 

 surveys, requiring primary triangles of great length of sides. A revolving 

 motion might be given to the lanterns, so as to make the light transmitted 

 from them visible from many different stations within short intervals of 

 time. Their simplicity, and the ease with which they are mauaged, would 

 perhaps give them, for such purposes, a great advantage over the Drummond 

 or Bade lights, even though they be not so brilliant as the latter. 



The heliotrope, which he employed in the day time, was made by order of 

 Mr. llassler, at the instrument shop of the coast survey office. It was a 

 rectangular parallcllogram of good German plate glass, 14 by l£ inch in size, 

 giving an area of reflecting surface of 2 T \£j square in. This also was seen at 

 the distance of 36 miles. 



SELF-ACTING CIRCULAR DIVIDING ENGINE. 



At one of the recent meetings of the Astronomical Society, a papei bj 

 W. SlMMS, Esq., was read describing a Self-acting Circular Dividing Engine. 

 The engine, in general arrangement and construction, is similar tu that made 

 by Mr. E. Troughton, though there are several additions ami peculiarities, 

 which are pointed out. The circle or engine-plate is of gun-metal, 16 inches 

 in diameter, and was cast in one entire piece, teeth being ratched upon its 

 edge. The centre of the engine-plate is so arranged that it can he entered 

 by the axis of the instrument to be divided, and the work by this means 

 brought down to bear upon the surface of the engine-plate, which arrange- 

 ment prevents the necessity of separating the part intended to receive the 

 divisions from its axis, &c, a process both troublesome and dangerous. 

 Upon the surface, and not far from the edge of the engine plate, arc two 

 sets of divisions to spaces of five minutes, one set being in silver and the 

 other strongly cut upon the gun-metal face. There are also as many teeth 

 upon the edge as there are divisions upon the face of the engine-plate, 

 namely, 4320, and consequently one revolution of the endless screw moves 

 through a space of five minutes. The silver ring was divided according to 

 Troughton's method, with some slight variations. In this operation it 

 seemed to the authors the safer course to divide the circle completely, and 

 then to use a single cutter for ratching the edge ; and he believes that the 

 teeth upon the edge have been cut as truly as the original divisions them- 

 selves. Another important arrangement is, that the engine is self-acting and 

 requires no personal exertion or superintendence, nothing being necessary 

 but the winding up of the machine, or rather the raising of a weight which, 

 by its descent, communicates motion to the dividing engine. The machinery 

 is so arranged that it can be used or dispensed with at pleasure, there being 

 some cases in which a superintending hand is desirable. The author then 

 proceeds with a description of the machinery, as represented in the drawings 

 accompanying his paper, and draws attention to the contrivance by which 

 the engine can discharge itself from action when it has completed its work. 

 He concluded by observing that the machinery is simple, by no means ex- 

 pensive, can be made by an ordinary workman, is adapted to all the engines 

 now in existence, which are moved by an endless screw, lessens the labour 

 of the artist and increases the accuracy of the graduated instrument. 



COATING METAL. 



William Henry Fox Talbot, of Laycock Abbey, Esq., has obtained a 

 patent for " improvements in coating or covering mttals with other metals." 

 Patent dated November 25, 1842. The specification of Mr. Talbot's present 

 patent discloses no new principle in the art of metallic precipitation ; but it 

 supplies some very useful improvements in its manipulative details. — 1. To 

 prepare metal articles for gilding, Mr. Talbot dips them in a weak solution 

 of silver in hypo-sulphate of soda. 2. To prepare an article for either gild- 

 ing or silvering, he first cleans it well, then connects it to one of the wires of 

 a voltaic battery, next plunges both poles into a vessel filled with some acid 

 solution, which, decomposing the water, the hydrogen is given oft" by the 

 article intended to be gilt or silvered. After a little time the article is 

 detached from the battery, and thrown into a solution of gold or silver, 

 where it speedily acquires the required coating. 3. To gild metallic articles, 

 he makes use of a mixed solution of gold, and any one of the baser metals, 

 with the exception of mercury, which would separate the gold. 4. He also 

 uses for gilding a solution of chloride of gold, mixed with a solution of 

 boracic acid, the latter having the effect of greatly improving the colour. 5. 

 To remove the dark tint which metallic articles sometimes acquire when 

 dipped in a solution of gold, they are immersed in a very weak solution of 

 nitrate of mercury. Any mercury which may adhere is afterwards removed 

 by an acid, assisted by voltaic action. And, 6. When in silvering an article, 

 the solution of silver ceases to impart any addition to the coating (in conse- 

 quence of the coating and the solution becoming of identical properties), Mr. 

 Talbot dips it into a different solution of silver, or into a solution of some 

 other metal, after which he replaces it in the first solution, when it is found 

 to act with the same energy as at first. The same method of alternate 

 dipping is also applicable to solutions of gold. — -Mechanic's Magazine. 



OXIDES OF METAL. 



John Mcllins, of Battersea, Surrey, surgeon, has obtained a patent for 

 " certain improvements in making oxides of metals, in separating silver and 

 other metals from their compounds with other metals, and in making white 

 lead, sugar of lead, and other salts of lead, and salts of other metals." — 

 Patent dated October 27, 1842. — Mr. Mullins's improvements are six in 

 number. First, he produces oxides of lead and other metals by forcing 

 currents of atmospheric air, or oxygen gas, through masses of the metal in a 

 melted state, " heated to the temperature of their respective points of oxida- 

 tion," and then skimming oft' the oxides from the surface. Second, to make 

 white lead he exposes the oxide of lead obtained by the preceding process, 

 which is stated to be much superior to the ordinary litharge and vitrified 



