JOG

DRAWING INSTRUMENTS—GAYARD’S PENTAGRAPIT.

Claps X.

whole length, the upper side of each being divided into100 parts. The under side of one is divided into 315parts, 314 of which are equal, the remaining part beingequal to OTG, and the relation existing between the divi-sions above and below, the lines being that of thediameter to the circumference of the circle.

The under side of the second line is divided into 89parts, 88 of which are equal, the remaining one equal to0*6:23. On the diameter of a circle being given, on theupper side, the side of the square whose area is equal tothat of the circle of that diameter, is read at the samepoint on the under side.

The under side of the third line is divided into 283parts, of which 282 are equal, and the other is equal to0*095. The relation existing between these lines at thesame point, is that of the circumference of a circle on theupper side, to the side of the square (to one place ofdecimals) equal in area to the area of the circle.

The reverse side of the scale is occupied by scales ofequal parts.

It is understood that Mr. Graham has arranged otherlines, showing the relation existing between the area ofthe circle when the diameter is given; and another givingthe area when the circumference is given.

Matthias (No. 395, p. 451) exhibits an instrument fordividing a given line quickly into any number of equalparts, less than 100, by a method susceptible of more ex-tended use. The principle of the instrument is that of anangle and parallel lines, the angle being formed by thetwo legs of the instrument, which may be opened to thedistance of 20 inches, any space less than which can bedivided; it is made of ivory.

Horne, Thorntiiwaite, and Wood (No. 220, pp. 434,435,) exhibit Tebay’s universal planing-rule, the noveltyconsisting in the arrangement of the division of the oddand even scales; by continuing the graduation to theedges, the necessity of making use of dividing compassesis obviated.

Gavaud (France, No. 235, p. 1197) exhibits improvedpentagraphs; the improvements, which consist principallyin a better arrangement of the steadying weight of thepivot, and the larger size of the wheels, add greatly to thesmooth working of the instrument, so much so that evenpersons unaccustomed to its use may produce smooth andunbroken lines. In the hands of Madame Gavard it per-formed several beautiful tracings of great delicacy anddifficulty, among which we may specially mention a mapof France , showing with great distinctness the depart-ments, comprised within two inches square. The steadi-ness of the instrument when in use is very greatlyincreased by the improvements of M. Gavard.

Gavard also exhibits a beam compass of most finishedworkmanship, and an instrument for drawing fromnature by mechanical means. A telescope with a crosswire in its focus is suspended in a jimbal frame, near theeye, and so as to keep the position of the eye nearlyfixed. It is so balanced and so lightly bung as to allowthe most perfect freedom of motion, and the cross of thewires being carried along every part of the outliue of theobject.

The object end of the telescope is suspended over apulley on a vertical support, by a silk line, which is con-ducted to the base of one support, and thence along a hori-zontal bar, to a pencil-holder sliding on the bar. Thusany movement in the vertical direction is traced on paper.To trace the horizontal movements in like manner, theupright support and the horizontal bar are made move-able on rollers to the right and left. The instrument isof most delicate execution, and works with perfectsmoothness. As specimens of its performance are exhi-bited a tracing of a ceiling of the Luxembourg , of singu-lar complexity; and a series of outlines, in illustration ofthe interior of the Palace of Versailles , with its rich andelaborate decorations, which are executed with exquisitefidelity and delicacy.

Ry adapting a microscope instead of a telescope to thejimbal frame, the outlines of a microscopic object, as ofan insect, wood section, &e., can, in like manner, betraced with perfect fidelity, and on any scale. Honour-able Mention was awarded to M. Gavard.

Luttig (Prussia, No. 81, p. 1053) exhibits severalcases of well-made drawing instruments, some in Germansilver and some in brass. The Jury awarded HonourableMention to M. Liittig.

Reifler (Bavaria, ’ No. 34, p. 1100) exhibits a case ofdrawing instruments; and Honourable Mention wasawarded by the Jury for his new method of fixing thetwo parts of a compass together by means of plane sur-faces with steadying pins and screws.

IIommel-Esser (Switzerland , No. 81, p. 1272) hasexhibited drawing instruments, distinguished for the carewith which the most minute details have been finished.A Prize Medal was awarded to this exhibitor.

Gysi (Switzerland , No. 85, p. 1272) has exhibiteddrawing instruments. The remarks applicable to the pre-ceding exhibitor, apply equally to these, and it may heobserved, that the steel used by both exhibitors is of thefinest quality and extremely well tempered. A PrizeMedal was awarded to this exhibitor.

Kern (Switzerland , Nos. 88 and 92, p. 1272) exhibitssome well-made drawing instruments, which, in commonwith those of the Swiss exhibitors, are made in differentparts, which can be readily separated and cleaned withease. The Jury considered Mr. Kern as deservingHonourable Mention.

Imperial Ijorsk Works (Russia , No. 109, p. 1372)exhibit a full set of twenty-seven drawing instruments,comprising eleven different articles 5 inches in length; aset comprising ten pieces of 3 inches in length, andmounted in silver.

The following drawing instruments are exhibitedmounted in brass: a full set of twenty-four pieces; a setof eleven pieces 5 inches in length; and a set of tenpieces 3 inches in length.

The following pocket instruments are exhibited:—Folding or silver-mounted compasses; brass compasses insilver sheath; and several other compasses mounted inbrass, some furnished with pencil tubes, and mostly fold-ing up. All these instruments are well made, and includethe recent improvements; they deserve very HonourableMention.

Viberg (Sweden , No. 14, p. 1350) exhibits two smallcases of drawing instruments, containing each a protract-ing semi-circle, a pair of large steel pointed compasses,two smaller for steel pens on exchangeable pencil points,and a steel ruling pen. They are very neatly made.

Ltttman (Norway , No. 15, p. 1350) is stated in theCatalogue to have exhibited drawing instruments, butcareful search being made for them, they were not foundamong the objects in this compartment of the Exhibition.(See Microscopes, levels).

Nif.tzcumann and Vaccani (Prussia, No. 700, p. 1089)exhibit many sets of drawing instruments, of an exceed-ingly low price. The Jury awards Honourable Mentionfor cheapness.

Rociietti (Austria , No. 130, p. 1014) exhibits a caseof drawing instruments of sixteen pieces, compasses, &c.,of brass and steel, of very elegant construction. Thereis no protracter, ruler, or scale.

Penrose (No. 318, p. 443) has exhibited registeredscrew and sliding helicograplis for drawing volutes, scrollwork, and spirals of various kinds. The outline may bedrawn on paper by means of an impression obtained fromthe disc by transfer paper, either -with ink or pencil bythe sliding helicopraph. For a description of these deli-cate and well-constructed instruments see the IllustratedCatalogue.

A Prize Medal was awarded to Mr. Penrose.

Orreries, Planetariums , and Astronomical Machines.

It is a matter of regret that the time and ingenuitywhich have been devoted to the several machines of thisclass in the Exhibition, have not been better directed.Those exhibited do not indicate any improvement overthe many which have been constructed, one only, per-haps, excepted, viz., a vertical orrery of large dimensions,made by a working man, after his own design, and it isunderstood, without ever having seen an orrery of anykind.

The time, ingenuity, and expense, devoted to machines