436
Class 10.—PHILOSOPHICAL, MUSICAL, HOKOLOGICAL,North, North Central, and South Central Galleries.
[Unitep
number of rays of light, but, on looting through a tele-scope, it takes in as many more rays in proportion as theobject-glass is larger than the pupil itself, and the objectappears as brilliant as it would were the pupil of the eyeto be enlarged to the size of the objeet-glass.—J. G.]
Chemical pottery wares. Complete apparatus for dis-tillation and condensation. Manufactured in terra cottachemical-stone ware, to stand great heat, and lined withacid-proof glaze.
Astronomical telescope, inches in diameter, mountedon an equatorial stand.
Astronomical telescope, 2| inches in diameter, mountedon a pillar-aud-claw stand.
Improved microscopes, with new method of illumina-tion. Improved photographic camera obscuras.
254a Reade, Rev. J. 13., F.R.S., Stone Vicarage , Aylesbury—Inventor.
Positive solid eye-pieces. (Main Avenue West.)
The solid eye-piece (see the following cut) consists of twodouble convex lenses, c and e, of crown glass, with an inter-mediate double concave lens, d, of flint, having the contact
ya, a
Reade’s Solid Eye-piece.
surfaces cemented together. The cap, b, contains a smalleye-hole, a. Its novelty consists in its construction, whichsecures a large and flat field of view, together with theremoval of spherical and chromatic aberration. In con-sequence of the purity of its achromatism, the webs ofthe transit instrument and micrometer are seen as fineblack lines, and hence it is found by experiment thatobservations are made more perfectly than with the com-mon positive eye-piece which is not achromatic. Nolight is lost, as in the usual construction, by inner re-flections, and there is no formation of the false image or“ ghost” of planets and the brighter stars. From thefollowing data the curves of the lenses may be determinedfor a given focal length.
Index of refraction of flint . . 1-600
Index of refraction of crown . . 1 • 523
Ratio of dispersive powers . . 0-657Thickness of flint lens . . . 0-775 x/.where / = whole focal length for parallel rays.
256 Hudson, Frederick Thomas, Greenwich —
Producer and Designer.
Microscopic objects—being minute parts of animal,vegetable, and mineral tissues, and structures, preparedfor examination by the microscope.
257 Varley & Son, 1 Charles Street , Clarendon
Square— Inventors and Makers.
Graphic telescopes, by which general views or imagesof objects, may be accurately traced, of any size.
Reversing camera, by which pictures or objects maybe traced the reverse way.
Microscope, in which the moveable stage is kept parallelto one position whilst moved about in any direction.
Reflecting telescopes.
Model of the apparatus for mounting together andchanging three small speculums of large Gregorian tele-scopes, so as not to lose sight of the object; thus the
power may be doubled, or quadrupled, or reduced withoutloss of time.
Air-pump, with crank motion and double-acting singl ebarrel. New double-acting exhausting air-pump.
Portable electrical apparatus: on moving the innertubes to and fro, the outer tube becomes charged in thesame manner as the Leyden phial.
258 Jackson, E. & W., 315 Oxford Street —Inventors.
Thin glass, used for microscopic purposes, and for thepolarization of light. Cells for mounting microscopieobjects. Slides for microscopic purposes; exhibited foreconomy in production.
259 Chadburn Brothers, Sheffield and Liverpool —Manufacturers.
Specimens of glass in the rough state, suitable f° rspectacles.
Glass, cut round and oval, ready for cementing on theblocks.
A block of glasses ready for grinding, being plane oiparallel.
A block of glasses ground to the required radius. Tn efocus of the glass depending on the radius of the lap inwhich they are ground. ,
A lap, 12 inches radius; glasses when ground on bothsides in it, are 12 inches focus.
A block of glasses, ground and polished, ready to b etaken off. Tool used for polishing the glasses.
A block of concave glasses finished; being cemented mthe lap, they are ground hollow.
Glasses ready for fitting into spectacles. The exhibitorsgrind 750 dozen per week, on the average.
Provisionally registered portable barometer. The in*"provement consists in making the cistern of glass (whichis covered) with a flexible cover, which can be pressedown, so as to prevent the mercury oscillating when thebarometer is carried about or packed for travelling.
Optical lenses, of various kinds. Spectacles—readingand magnifying glasses, &c. Opera-glasses and snia
telescopes. Day or night ship and signal telescope®-Large and portable achromatic telescopes. Simple an^compound microscopes. Magic lanterns and views. L<mera-obscuras and diagonal mirrors. Agricultural ansurveyors’ levels, &c. Horse-shoe and other magne ^Steam and vacuum gauges. Barometers, &c. ® a .. > s
and window syringes. Galvano-electric machines. Shipberth or side illuminators and ventilators. WorkWsmodels of steam-engines, &c. Craig’s charactograph.
260 Bond, J. W., Emma Street , Ann’s Place , HackneyRoad —Inventor and Manufacturer. ,
Natural objects, prepared in Canada balsam, f° r ‘oxyhydrogen microscope.
263 Abraiiam, Abraham, & Co., 20 Lord Street,Liverpool —Manufacturers.
Trinoptric prismatic lantern, with apparatus for makmgoxygen gas, viz.: gas bag, retort, and purifier, invenby the Rev. St. Vincent Beechy. It combines the powof three lanterns, with one small lamp of intense brightne •A disc of 25 feet for each tube may be obtained, and eadisc is capable of being darkened to any required exte >without shadow on any portion of the picture. _ - 0 f
Dioptric prismatic lantern, producing two in henthree discs.
Compound microscope, exhibited for workmanship-
Portable sketching camera-obscura. In the 9? jj eUarrangement, a meniscus and prism are employed mof a lens and mirror, and a vivid flat picture is obtai
[The trinoptric and dioptric lanterns exhibited,are^the purpose of producing panoramic and other pie _generally displayed by means of the phantasmagoria ^terns and dissolving-view apparatus. The lamp eia ?is an oil-lamp, supplied with oxygen gas, on the pHof the Bude light.
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